顔写真

カワタ マサカド
河田 雅圭
Masakado Kawata
所属
高度教養教育・学生支援機構 教養教育院
職名
総長特命教授
学位
  • 農学博士(北海道大学)

  • 農学修士(北海道大学)

プロフィール

https://ochotona0.wixsite.com/mysite

経歴 6

  • 2023年4月 ~ 継続中
    東北大学 高度教養教育・学生支援機構 教養教育院 総長特命教授

  • 2001年4月 ~ 2023年3月
    東北大学 大学院生命科学研究科 教授

  • 2000年4月 ~ 2001年4月
    東北大学 大学院理学研究科 教授

  • 1997年5月 ~ 2000年3月
    東北大学 大学院理学研究科 助教授

  • 1990年6月 ~ 1997年4月
    静岡大学 教育学部 助教授

  • 1988年4月 ~ 1990年5月
    静岡大学 教育学部 助手

︎全件表示 ︎最初の5件までを表示

学歴 2

  • 北海道大学 農学研究科 農業生物学

    ~ 1987年6月30日

  • 帯広畜産大学 畜産学部 獣医学科

    1976年4月 ~ 1980年3月

委員歴 6

  • Ecological Research Associate Editor-in-Chief

    2011年1月 ~ 2013年3月

  • Ecological Research Editor-in-Chief

    2008年1月 ~ 2010年12月

  • Ecology Letters Editor,

    2002年7月 ~ 2007年12月

  • Population Ecology Editorial board

    1995年1月 ~ 2006年12月

  • The European Society for Evolution Editor, Journal of Evolutonary Biology

    1998年7月 ~ 2001年6月

  • Journal of Evolutonary Biology Editor,

    1998年7月 ~ 2001年6月

︎全件表示 ︎最初の5件までを表示

所属学協会 2

  • 日本進化学会

  • 日本生態学会

研究キーワード 5

  • 進化可能性

  • 生物多様性

  • ゲノム進化

  • 生態

  • 進化

研究分野 2

  • ライフサイエンス / 多様性生物学、分類学 / 進化生物学

  • ライフサイエンス / 生態学、環境学 / 生態学

受賞 3

  1. 第18回日本生態学会賞

    2020年3月 日本生態学会

  2. 木村資生記念学術賞

    2017年8月 公益信託進化学振興木村資生基金

  3. 日本進化学会学会賞

    2017年8月 日本進化学会

論文 157

  1. Detection of evolutionary conserved and accelerated genomic regions related to adaptation to thermal niches in Anolis lizards 査読有り

    Sakamoto,F, S. Kanamori, L. M. Díaz, A. Cádiz, Y. Ishii, K. Yamaguchi, S. Shigenobu, T. Nakayama, T. Makino, M. Kawata

    14 e11117 2024年3月

    DOI: 10.1002/ece3.11117  

  2. Transcriptomic signatures associated with underlying rapid changes in the early phase brain of bi-directional sex change in <i>Trimma okinawae</i>

    Katsunori Tamagawa, Tomoki Sunobe, Takashi Makino, Masakado Kawata

    10 231450 2023年12月6日

    出版者・発行元:None

    DOI: 10.1098/rsos.231450  

    eISSN:2054-5703

  3. Genetic differentiation and local adaptation of the Japanese honeybee, Apis cerana japonica 査読有り

    Wakamiya, T, T. Kamioka, Y. Ishii, J. Takahashi, R. T. Maeda, M. Kawata

    Ecology and Evolution 13 e10573 2023年9月

    DOI: 10.1002/ece3.10573  

  4. Environmental pH signals the release of monosaccharides from cell wall in coral symbiotic alga 査読有り

    Yuu Ishii, Hironori Ishii, Takeshi Kuroha, Ryusuke Yokoyama, Ryusaku Deguchi, Kazuhiko Nishitani, Jun Minagawa, Masakado Kawata, Shunichi Takahashi, Shinichiro Maruyama

    eLife 12 e80628 2023年8月18日

    出版者・発行元:None

    DOI: 10.7554/elife.80628  

    eISSN:2050-084X

  5. Twenty-year changes in the composition of a mixed stock of foraging green turtles in the Yaeyama Islands of Japan 査読有り

    Tomoko Hamabata, Masakado Kawata, Satomi Kondo, Ayumi Matsuo, Yoshihisa Suyama, Kazuyuki Suzuki, Kazunari Kameda

    Marine Ecology Progress Series 716 93-105 2023年8月10日

    DOI: 10.3354/meps14367  

  6. Differentially expressed genes associated with body size changes and transposable element insertions between <i>Caenorhabditis elegans</i> and its sister species, <i>C. inopinata</i>. 査読有り

    Kazuma Kawahara, Taruho Inada, Ryusei Tanaka, Mehmet Dayi, Takashi Makino, Shinichi Maruyama, Taisei Kikuchi, Asako Sugimoto, Masakado Kawata

    Genome Biology and Evolution 15 4 2023年4月18日

    出版者・発行元:None

    DOI: 10.1093/gbe/evad063  

    eISSN:1759-6653

  7. On the origin of appetite: GLWamide in jellyfish represents an ancestral satiety neuropeptide. 国際誌 査読有り

    Thoma, V, S. Sakai, K. Nagata, Y. Ishii, S. Maruyama, A. Abe, S. Kondo, M. Kawata, Shun Hamada, R. Deguchi, H. Tanimoto

    Proceedings of the National Academy of Sciences of the United States of America 120 2221493120 2023年4月

    DOI: 10.1073/pnas.2221493120  

  8. Draft genome of six Cuban Anolis lizards and insights into genetic changes during their diversification 査読有り

    Shunsuke Kanamori, Luis M. Díaz, Antonio Cádiz, Katsushi Yamaguchi, Shuji Shigenobu, Masakado Kawata

    BMC Ecology and Evolution 22 129 2022年11月4日

    出版者・発行元:None

    DOI: 10.1186/s12862-022-02086-7  

    eISSN:2730-7182

  9. Humanized substitutions of Vmat1 in mice alter amygdala-dependent behaviors associated with the evolution of anxiety 査読有り

    Daiki X. Sato, Yukiko U. Inoue, Nahoko Kuga, Satoko Hattori, Kensaku Nomoto, Yuki Morimoto, Giovanni Sala, Hideo Hagihara, Takefumi Kikusui, Takuya Sasaki, Yuji Ikegaya, Tsuyoshi Miyakawa, Takayoshi Inoue, Masakado Kawata

    iScience 25 (8) 104800-104800 2022年8月

    出版者・発行元:Elsevier BV

    DOI: 10.1016/j.isci.2022.104800  

    ISSN:2589-0042

  10. A new dwarf green anole (Squamata: Dactyloidae) of the Anolis carolinensisspecies group, from western Cuba 査読有り

    Luis M. Díaz, Antonio Cádiz, Karina Velazco, Masakado Kawata

    Caribbean Herpetology 1-16 2022年7月20日

    出版者・発行元:Caribbean Herpetology

    DOI: 10.31611/ch.84  

    eISSN:2333-2468

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    Green anoles of the Anolis carolinensis group are divided into the carolinensis and isolepis subgroups according to a consensus ofmolecular phylogenies. Species in the Anolis isolepis subgroup (A. altitudinalis, A. isolepis, A. oporinus, and A. toldo) are endemic to Cubaand the highest diversity is concentrated in forested areas of eastern Cuba. Here, we describe a new species of this subgroup from westernCuba based on genetic and morphological differences from other species. Our phylogenetic analysis, based on DNA sequences,includes all of the known species and suggests that the new species is more closely related to A. altitudinalis, A. oporinus, and A. toldothan to the widespread A. isolepis. In addition, we provide a new hypothesis on the taxonomic status of A. incredulus and recommendthat it no longer be considered as a species in the A. carolinensis group. Due to the lack of a diagnosis, and poor condition, of the onlyavailable specimen, we consider A. incredulus as a species inquirenda. New morphological and genetic data of recently collected specimensof A. oporinus and A. toldo will provide complementary information about these species known from one or a few specimens.

  11. Genes associated with hot defensive bee ball in the Japanese honeybee, Apis cerana japonica 査読有り

    Takahiro Kamioka, Hiromu C. Suzuki, Atsushi Ugajin, Yuta Yamaguchi, Masakazu Nishimura, Tetsuhiko Sasaki, Masato Ono, Masakado Kawata

    BMC Ecology and Evolution 22 (1) 31 2022年3月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1186/s12862-022-01989-9  

    eISSN:2730-7182

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    Abstract Background The Japanese honeybee, Apis cerana japonica, shows a specific defensive behavior, known as a “hot defensive bee ball,” used against the giant hornet, Vespa mandarinia. Hundreds of honeybee workers surround a hornet and make a “bee ball” during this behavior. They maintain the ball for around 30 min, and its core temperature can reach 46. Although various studies have been conducted on the characteristics of this behavior, its molecular mechanism has yet to be elucidated. Here, we performed a comprehensive transcriptomic analysis to detect candidate genes related to balling behavior. Results The expression levels of differentially expressed genes (DEGs) in the brain, flight muscle, and fat body were evaluated during ball formation and incubation at 46 °C. The DEGs detected during ball formation, but not in response to heat, were considered important for ball formation. The expression of genes related to rhodopsin signaling were increased in all tissues during ball formation. DEGs detected in one or two tissues during ball formation were also identified. Conclusions Given that rhodopsin is involved in temperature sensing in Drosophila, the rhodopsin-related DEGs in A. cerana japonica may be involved in temperature sensing specifically during ball formation.

  12. Deep learning increases the availability of organism photographs taken by citizens in citizen science programs 査読有り

    Yukari Suzuki-Ohno, Thomas Westfechtel, Jun Yokoyama, Kazunori Ohno, Tohru Nakashizuka, Masakado Kawata, Takayuki Okatani

    Scientific Reports 12 (1) 2022年1月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41598-022-05163-5  

    ISSN:2045-2322

    eISSN:2045-2322

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    <title>Abstract</title>Citizen science programs using organism photographs have become popular, but there are two problems related to photographs. One problem is the low quality of photographs. It is laborious to identify species in photographs taken outdoors because they are out of focus, partially invisible, or under different lighting conditions. The other is difficulty for non-experts to identify species. Organisms usually have interspecific similarity and intraspecific variation, which hinder species identification by non-experts. Deep learning solves these problems and increases the availability of organism photographs. We trained a deep convolutional neural network, Xception, to identify bee species using various quality of bee photographs that were taken by citizens. These bees belonged to two honey bee species and 10 bumble bee species with interspecific similarity and intraspecific variation. We investigated the accuracy of species identification by biologists and deep learning. The accuracy of species identification by Xception (83.4%) was much higher than that of biologists (53.7%). When we grouped bee photographs by different colors resulting from intraspecific variation in addition to species, the accuracy of species identification by Xception increased to 84.7%. The collaboration with deep learning and experts will increase the reliability of species identification and their use for scientific researches.

  13. Gene expression alterations from reversible to irreversible stages during coral metamorphosis 国際誌 査読有り

    Yuu Ishii, Masayuki Hatta, Ryusaku Deguchi, Masakado Kawata, Shinichiro Maruyama

    Zoological Letters 8 (1) 4-4 2022年1月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1186/s40851-022-00187-1  

    eISSN:2056-306X

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    <title>Abstract</title>For corals, metamorphosis from planktonic larvae to sedentary polyps is an important life event, as it determines the environment in which they live for a lifetime. Although previous studies on the reef-building coral <italic>Acropora</italic> have clarified a critical time point during metamorphosis when cells are committed to their fates, as defined by an inability to revert back to their previous states as swimming larvae (here referred to as the “point of no return”), the molecular mechanisms of this commitment to a fate remain unclear. To address this issue, we analyzed the transcriptomic changes before and after the point of no return by inducing metamorphosis of <italic>Acropora tenuis</italic> with Hym-248, a metamorphosis-inducing neuropeptide. Gene Ontology and pathway enrichment analysis of the 5893 differentially expressed genes revealed that G protein-coupled receptors (GPCRs) were enriched, including GABA receptor and Frizzled gene subfamilies, which showed characteristic temporal expression patterns. The GPCRs were then classified by comparison with those of <italic>Homo sapiens</italic>, <italic>Nematostella vectensis</italic> and <italic>Platynereis dumerilii</italic>. Classification of the differentially expressed genes into modules based on expression patterns showed that some modules with large fluctuations after the point of no return were biased toward functions such as protein metabolism and transport. This result suggests that in precommitted larvae, different types of GPCR genes function to ensure a proper environment, whereas in committed larvae, intracellular protein transport and proteolysis may cause a loss of the reversibility of metamorphosis as a result of cell differentiation.

  14. Genetic basis of orange spot formation in the guppy (Poecilia reticulata) 査読有り

    Mayuko Kawamoto, Yuu Ishii, Masakado Kawata

    BMC Ecology and Evolution 21 (1) 2021年12月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1186/s12862-021-01942-2  

    eISSN:2730-7182

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    <title>Abstract</title><sec> <title>Background</title> To understand the evolutionary significance of female mate choice for colorful male ornamentation, the underlying regulatory mechanisms of such ornamentation must be understood for examining how the ornaments are associated with “male qualities” that increase the fitness or sexual attractiveness of offspring. In the guppy (<italic>Poecilia reticulata</italic>), an established model system for research on sexual selection, females prefer males possessing larger and more highly saturated orange spots as potential mates. Although previous studies have identified some chromosome regions and genes associated with orange spot formation, the regulation and involvement of these genetic elements in orange spot formation have not been elucidated. In this study, the expression patterns of genes specific to orange spots and certain color developmental stages were investigated using RNA-seq to reveal the genetic basis of orange spot formation. </sec><sec> <title>Results</title> Comparing the gene expression levels of male guppy skin with orange spots (orange skin) with those without any color spots (dull skin) from the same individuals identified 1102 differentially expressed genes (DEGs), including 630 upregulated genes and 472 downregulated genes in the orange skin. Additionally, the gene expression levels of the whole trunk skin were compared among the three developmental stages and 2247 genes were identified as DEGs according to color development. These analyses indicated that secondary differentiation of xanthophores may affect orange spot formation. </sec><sec> <title>Conclusions</title> The results suggested that orange spots might be formed by secondary differentiation, rather than de novo generation, of xanthophores, which is induced by Csf1 and thyroid hormone signaling pathways. Furthermore, we suggested candidate genes associated with the areas and saturation levels of orange spots, which are both believed to be important for female mate choice and independently regulated. This study provides insights into the genetic and cellular regulatory mechanisms underlying orange spot formation, which would help to elucidate how these processes are evolutionarily maintained as ornamental traits relevant to sexual selection. </sec>

  15. Bee occurrence data collected in citizen science program “ Hanamaru‐Maruhana national census” in Japan 査読有り

    Yukari Suzuki‐Ohno, Jun Yokoyama, Tohru Nakashizuka, Masakado Kawata

    Ecological Research 36 (6) 1028-1036 2021年11月

    出版者・発行元:Wiley

    DOI: 10.1111/1440-1703.12261  

    ISSN:0912-3814

    eISSN:1440-1703

  16. The effect of the doublesex gene in body colour masculinization of the damselfly Ischnura senegalensis 査読有り

    Michihiko Takahashi, Genta Okude, Ryo Futahashi, Yuma Takahashi, Masakado Kawata

    Biology Letters 17 (6) 20200761-20200761 2021年6月

    出版者・発行元:The Royal Society

    DOI: 10.1098/rsbl.2020.0761  

    ISSN:1744-9561

    eISSN:1744-957X

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    Odonata species display a remarkable diversity of colour patterns, including intrasexual polymorphisms. In the damselfly ( <italic>Ischnura senegalensis</italic> ), the expression of a sex-determining transcription factor, the <italic>doublesex</italic> ( <italic>Isdsx</italic> ) gene is reportedly associated with female colour polymorphism (CP) (gynomorph for female-specific colour and andromorph for male-mimicking colour). Here, the function of <italic>Isdsx</italic> in thoracic coloration was investigated by electroporation-mediated RNA interference (RNAi). RNAi of the <italic>Isdsx</italic> common region in males and andromorphic females reduced melanization and thus changed the colour pattern into that of gynomorphic females, while the gynomorphic colour pattern was not affected. By contrast, RNAi against the <italic>Isdsx</italic> long isoform produced no changes, suggesting that the <italic>Isdsx</italic> short isoform is important for body colour masculinization in both males and andromorphic females. When examining the expression levels of five genes with differences between sexes and female morphs, two melanin-suppressing genes, <italic>black</italic> and <italic>ebony</italic> , were expressed at higher levels in the <italic>Isdsx</italic> RNAi body area than a control area. Therefore, the <italic>Isdsx</italic> short isoform may induce thoracic colour differentiation by suppressing <italic>black</italic> and <italic>ebony</italic> , thereby generating female CP in <italic>I. senegalensis.</italic> These findings contribute to the understanding of the molecular and evolutionary mechanisms underlying female CP in Odonata.

  17. Detection of genes positively selected in Cuban Anolis lizards that naturally inhabit hot and open areas and currently thrive in urban areas 査読有り

    Shunsuke Kanamori, Antonio Cádiz, Luis M. Díaz, Yuu Ishii, Takuro Nakayama, Masakado Kawata

    Ecology and Evolution 11 (4) 1719-1728 2021年2月15日

    出版者・発行元:Wiley

    DOI: 10.1002/ece3.7161  

    ISSN:2045-7758

    eISSN:2045-7758

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    Species of Anolis lizards of the West Indies that naturally inhabit hot and open areas also tend to thrive in urban areas. In this study, transcriptome was sequenced for nine species of Cuban Anolis lizards that are closely related to each other, but inhabit different thermal microhabitats. Using PAML and HyPhy software, we attempted to identify genes and amino acid sites under positive selection in the common ancestral branch of A. porcatus and A. allisoni, and the branch of A. sagrei, which inhabit hot and open areas, and thrive in urban areas. Although there were no genes where positive selection was commonly detected on both of the tested branches, positive selection was detected in genes involved in the stress response (e.g., DNA damage and oxidative stress) and cardiac function, which could be related to adaptive evolution of tolerance to heat or ultraviolet radiation, on both branches. These findings suggest that adaptive evolution of the response to stress caused by heat or ultraviolet radiation might have occurred in ancestors of Anolis species inhabiting hot and open areas and might be related to the current thriving in urban areas of them.

  18. Identification of a reptile lyssavirus in Anolis allogus provided novel insights into lyssavirus evolution 国際誌 査読有り

    Masayuki Horie, Hiroshi Akashi, Masakado Kawata, Keizo Tomonaga

    Virus Genes 57 (1) 40-49 2021年2月7日

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1007/s11262-020-01803-y  

    ISSN:0920-8569

    eISSN:1572-994X

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    Lyssaviruses (genus Lyssavirus) are negative-strand RNA viruses belonging to the family Rhabdoviridae. Although a lyssa-like virus (frog lyssa-like virus 1 [FLLV-1]), which is distantly related to lyssaviruses, was recently identified in frogs, a large phylogenetic gap exists between those viruses, and thus the evolution of lyssaviruses is unclear. In this study, we detected a lyssa-like virus from publicly available RNA-seq data obtained using the brain and skin of Anolis allogus (Spanish flag anole), which was designated anole lyssa-like virus 1 (ALLV-1), and determined its complete coding sequence. Via mapping analysis, we demonstrated that ALLV-1 was actively replicating in the original brain and skin samples. Phylogenetic analyses revealed that ALLV-1 is more closely related to lyssaviruses than FLLV-1. Overall, the topology of the tree is compatible with that of hosts, suggesting the long-term co-divergence of lyssa-like and lyssaviruses and vertebrates. The ψ region, which is a long 3' untranslated region of unknown origin present in the G mRNA of lyssaviruses (approximately 400-700 nucleotides), is also present in the genome of ALLV-1, but it is much shorter (approximately 180 nucleotides) than those of lyssaviruses. Interestingly, FLLV-1 lacks the ψ region, suggesting that the ψ region was acquired after the divergence of the FLLV-1 and ALLV-1/lyssavirus lineages. To the best of our knowledge, this is the first report to identify a lyssa-like virus in reptiles, and thus, our findings provide novel insights into the evolution of lyssaviruses.

  19. Estimating possible bumblebee range shifts in response to climate and land cover changes 査読有り

    Yukari Suzuki-Ohno, Jun Yokoyama, Tohru Nakashizuka, Masakado Kawata

    Scientific Reports 10 (1) 19622 2020年11月

    出版者・発行元:None

    DOI: 10.1038/s41598-020-76164-5  

    eISSN:2045-2322

  20. Natal Origin Identification of Green Turtles in the North Pacific by Genome-Wide Population Analysis With Limited DNA Samples 査読有り

    Tomoko Hamabata, Ayumi Matsuo, Mitsuhiko P. Sato, Satomi Kondo, Kazunari Kameda, Isao Kawazu, Takuya Fukuoka, Katsufumi Sato, Yoshihisa Suyama, Masakado Kawata

    Frontiers in Marine Science 7 658 2020年8月7日

    出版者・発行元:Frontiers Media SA

    DOI: 10.3389/fmars.2020.00658  

    eISSN:2296-7745

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    Although studies using genome-wide single nucleotide polymorphisms (SNPs) are growing in non-model species, it is still difficult to prepare sufficient high-quality genomic DNA (gDNA) for population genomic analyses in many wild species. In this study, we first analyzed the population structure of green turtles in the North Pacific; four regions in Japan (the Yaeyama, Okinawa, Amami, and Ogasawara Islands), the Southeast Asia, Taiwan, the Federated States of Micronesia, the Republic Marshall Islands, and the Central or Eastern Pacific (C/E Pacific) using ≃1 ng of gDNA from green turtle field samples – including ones from dead carcasses – and multiplexed inter-simple sequence repeat (ISSR) genotyping by sequencing (MIG-seq). In addition, we explored whether the genome-wide SNP data narrowed down the natal origins of foraging turtles that were difficult to identify by mitochondrial DNA (mtDNA) haplotype alone. The overall nesting population structure observed from genome-wide SNPs was consistent with results from mtDNA, and the population isolation of the C/E Pacific and Ogasawara Islands from the other North Pacific populations was highlighted. However, the population boundaries among the Northwestern Pacific, other than those of the Ogasawaras, were not clear. The uniqueness of the Ogasawara population in genome-wide SNP data enabled the identification of turtles that were more likely to have been born on the Ogasawara Islands. Our results show that genome-wide SNP data are more practical in identifying the natal origins of turtles that were difficult determine by the conventional mtDNA-basis mixed stock analysis. This study also showed that MIG-seq can be expected to meet the potential demand to utilize many preserved or fragmented gDNA samples for population genomics in many marine megafaunas for which sample collections are difficult.

  21. Contradictory effects of leaf rolls in a leaf-mining weevil 査読有り

    Chisato Kobayashi, Kazunori Matsuo, Masakado Kawata

    Scientific Reports 10 (1) 12180 2020年8月

    出版者・発行元:Springer Science and Business Media LLC

    DOI: 10.1038/s41598-020-69002-1  

    eISSN:2045-2322

  22. Genetic factors for short life span associated with evolution of the loss of flight ability 査読有り

    Atsushi Ikemoto, Daiki X. Sato, Takashi Makino, Masakado Kawata

    Ecology and Evolution 10 (12) 6020-6029 2020年5月29日

    出版者・発行元:Wiley

    DOI: 10.1002/ece3.6342  

    ISSN:2045-7758

    eISSN:2045-7758

  23. Environmental factors explain spawning day deviation from full moon in the scleractinian coral Acropora. 査読有り

    Sakai, Y., M. Hatta, S. Furukawa, M. Kawata, N. Ueno, S. Maruyama

    Biology Letters 16 20190760 2020年1月

  24. Genetic segregation for male body coloration and female mate preference in the guppy. 査読有り

    Aya Sato, Masakado Kawata

    BMC Research Notes 19 220 2020年1月

  25. Human-specific mutations in VMAT1 confer functional changes and multi-directional evolution in the regulation of monoamine circuits. 国際誌 査読有り

    Daiki X Sato, Yuu Ishii, Tomoaki Nagai, Kazumasa Ohashi, Masakado Kawata

    BMC evolutionary biology 19 (1) 220-220 2019年12月2日

    DOI: 10.1186/s12862-019-1543-8  

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    BACKGROUND: Neurochemicals like serotonin and dopamine play crucial roles in human cognitive and emotional functions. Vesicular monoamine transporter 1 (VMAT1) transports monoamine neurotransmitters, and its variant (136Thr) is associated with various psychopathological symptoms and reduced monoamine uptake relative to 136Ile. We previously showed that two human-specific amino acid substitutions (Glu130Gly and Asn136Thr/Ile) of VMAT1 were subject to positive natural selection. However, the potential functional alterations caused by these substitutions (Glu130Gly and Asn136Thr) remain unclear. To assess functional changes in VMAT1 from an evolutionary perspective, we reconstructed ancestral residues and examined the role of these substitutions in monoamine uptake in vitro using fluorescent false neurotransmitters (FFN), which are newly developed substances used to quantitatively assay VMATs. RESULTS: Immunoblotting confirmed that all the transfected YFP-VMAT1 variants are properly expressed in HEK293T cells at comparable levels, and no significant difference was seen in the density and the size of vesicles among them. Our fluorescent assays revealed a significant difference in FFN206 uptake among VMAT1 variants: 130Glu/136Asn, 130Glu/136Thr, and 130Gly/136Ile showed significantly higher levels of FFN206 uptake than 130Gly/136Asn and 130Gly/136Thr, indicating that both 130Glu and 136Ile led to increased neurotransmitter uptake, for which 136Thr and 136Asn were comparable by contrast. CONCLUSIONS: These findings suggest that monoamine uptake by VMAT1 initially declined (from 130Glu/136Asn to 130Gly/136Thr) in human evolution, possibly resulting in higher susceptibility to the external environment of our ancestors.

  26. Single-cell genomics unveiled a cryptic cyanobacterial lineage with a worldwide distribution hidden by a dinoflagellate host 査読有り

    Nakayama,T, M. Nomura, Y. Takano, G. Tanifuji, K. Shiba, K. Inaba, Y. Inagaki, M. Kawata

    Proceedings of the National Academy of Sciences of the United States of America 116 (32) 15973-15978 2019年8月

    DOI: 10.1073/pnas.1902538116  

  27. Local adaptation stops where ecological gradients steepen or are interrupted. 査読有り

    Bridle, J, M. Kawata, R. Butlin

    Evolutionary Applications 12 1449-1462 2019年8月

  28. Global Shifts in Gene Expression Profiles Accompanied with Environmental Changes in Cnidarian-Dinoflagellate Endosymbiosis. 国際誌 査読有り

    Yuu Ishii, Shinichiro Maruyama, Hiroki Takahashi, Yusuke Aihara, Takeshi Yamaguchi, Katsushi Yamaguchi, Shuji Shigenobu, Masakado Kawata, Naoto Ueno, Jun Minagawa

    G3 (Bethesda, Md.) 9 (7) 2337-2347 2019年7月9日

    DOI: 10.1534/g3.118.201012  

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    Stable endosymbiotic relationships between cnidarian animals and dinoflagellate algae are vital for sustaining coral reef ecosystems. Recent studies have shown that elevated seawater temperatures can cause the collapse of their endosymbiosis, known as 'bleaching', and result in mass mortality. However, the molecular interplay between temperature responses and symbiotic states still remains unclear. To identify candidate genes relevant to the symbiotic stability, we performed transcriptomic analyses under multiple conditions using the symbiotic and apo-symbiotic (symbiont free) Exaiptasia diaphana, an emerging model sea anemone. Gene expression patterns showed that large parts of differentially expressed genes in response to heat stress were specific to the symbiotic state, suggesting that the host sea anemone could react to environmental changes in a symbiotic state-dependent manner. Comparative analysis of expression profiles under multiple conditions highlighted candidate genes potentially important in the symbiotic state transition under heat-induced bleaching. Many of these genes were functionally associated with carbohydrate and protein metabolisms in lysosomes. Symbiont algal genes differentially expressed in hospite encode proteins related to heat shock response, calcium signaling, organellar protein transport, and sugar metabolism. Our data suggest that heat stress alters gene expression in both the hosts and symbionts. In particular, heat stress may affect the lysosome-mediated degradation and transportation of substrates such as carbohydrates through the symbiosome (phagosome-derived organelle harboring symbiont) membrane, which potentially might attenuate the stability of symbiosis and lead to bleaching-associated symbiotic state transition.

  29. Invasive invertebrates associated with highly duplicated gene content. 査読有り

    Makino, T, M. Kawata

    Molecular Ecology 28 1652-1663 2019年4月

    DOI: 10.1111/mec.15019  

  30. Acoustic emissions of Sorex unguiculatus (Mammalia: Soricidae): assessing the echo-based orientation hypothesis. 査読有り

    Sanchez, L, S. D. Ohdachi, A. Kawahara, L. M. Echenique-Diaz, S. Maruyama, M. Kawata

    Ecology and Evolution 116 2118-2123 2019年2月

    DOI: 10.1002/ece3.4930  

  31. Draxin regulates hippocampal neurogenesis in the postnatal dentate gyrus by inhibiting DCC-induced apoptosis 査読有り

    Hiroshi Tawarayama, Hirohisa Yamada, Ruhul Amin, Yuiko Morita-Fujimura, Helen M. Cooper, Yohei Shinmyo, Masakado Kawata, Shuntaro Ikawa, Hideaki Tanaka

    Scientific Reports 8 (1) 840 2018年12月1日

    出版者・発行元:Nature Publishing Group

    DOI: 10.1038/s41598-018-19346-6  

    ISSN:2045-2322

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    Hippocampal neurogenesis in the dentate gyrus (DG) is controlled by diffusible molecules that modulate neurogenic processes, including cell proliferation, differentiation and survival. To elucidate the mechanisms underlying hippocampal neurogenesis, we investigated the function of draxin, originally identified as a neural chemorepellent, in the regulation of neuronal survival in the DG. Draxin was expressed in Tbr2 (+) late progenitors and NeuroD1 (+) neuroblasts in the dentate granule cell lineage, whereas expression of its receptor DCC (deleted in colorectal cancer) was mainly detectable in neuroblasts. Our phenotypic analysis revealed that draxin deficiency led to enhanced apoptosis of DCC-expressing neuroblasts in the neurogenic areas. Furthermore, in vitro assays using a hippocampal neural stem/progenitor cell (HNSPC) line indicated that draxin inhibited apoptosis in differentiating HNSPCs, which express DCC. Taken together, we postulate that draxin plays a pivotal role in postnatal DG neurogenesis as a dependence receptor ligand for DCC to maintain and promote survival of neuroblasts.

  32. Genetic and plastic variation in opsin gene expression, light sensitivity, and female response to visual signals in the guppy. 査読有り

    Sakai, Y, S. Kawamura, M. Kawata

    Proceedings of the National Academy of Sciences of the United States of America 115 12247-12252 2018年11月

    DOI: 10.1073/pnas.1706730115  

  33. Impact of sexually antagonistic genital morphologies on female reproduction and wild population demography. 査読有り

    Takami, Y, T. Fukuhara, J. Yokoyama, M. Kawata

    Evolution 72 2449-2461 2018年10月

    DOI: 10.1111/evo.13603  

  34. Factors affecting interspecific differences in genetic divergence among populations of Anolis lizards in Cuba 査読有り

    Cádiz, A, N. Nagata, L. Díaz, Y. Suzuki-Ohno, L.Echenique-Díaz, H. Akashi, T. Makino, M. Kawata

    Zoological Letters 4 21 2018年8月

    DOI: 10.1186/s40851-018-0107-x  

  35. Positive and balancing selection on SLC18A1 gene associated with psychiatric disorders and human-unique personality traits. 査読有り

    Sato, D. X, M. Kawata

    Evolution Letters 2 499-510 2018年8月

    DOI: 10.1002/evl3.81  

  36. Evolution of gustatory receptor gene family provides insights into adaptation to diverse host plants in nymphalid butterflies 査読有り

    Suzuki, H. C, K. Ozaki, T. Makino, H. Uchiyama, S. Yajima, M. Kawata

    Genome Biology and Evolution 10 1351-1362 2018年5月

    DOI: 10.1093/gbe/evy093  

  37. Comparisons of behavioural and TRPA1 heat sensitivities in three sympatric Cuban Anolis lizards 査読有り

    Hiroshi D. Akashi, Shigeru Saito, Antonio Cádiz Díaz, Takashi Makino, Makoto Tominaga, Masakado Kawata

    Molecular Ecology 27 (9) 2234-2242 2018年5月1日

    出版者・発行元:Blackwell Publishing Ltd

    DOI: 10.1111/mec.14572  

    ISSN:1365-294X 0962-1083

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    Thermal tolerances of organisms play a role in defining geographic ranges and occurrence of species. In Cuba, three sympatric species of Anolis lizards (Anolis allogus, Anolis homolechis and Anolis sagrei) inhabit different thermal microhabitats. A previous study found that these species showed distinct gene expression patterns in response to temperature stimuli, suggesting the genetically distinct thermal physiology among species. To investigate whether the Anolis species inhabiting locally distinct thermal habitats diverge their thermal tolerances, we first conducted behavioural experiments to analyse the temperatures at which the three Anolis species escape from heat source. Then, for each of the three species, we isolated cDNA encoding a putative molecular heat sensor, transient receptor potential ion channel ankyrin 1 (TRPA1), which has been suggested to play a role on eliciting behavioural responses to heat stimuli. We performed electrophysiological analysis to quantify activation temperature of Anolis TRPA1 to see whether the pattern of divergence in TRPA1 responses is congruent with that of divergence in behavioural responses. We found that temperatures triggering behavioural and TRPA1 responses were significantly lower for shade-dwelling species (A. allogus) than for sun-dwelling species (A. homolechis and A. sagrei). The ambient temperature of shade habitats where A. allogus occurs stays relatively cool compared to that of open habitats where A. homolechis and A. sagrei occur and bask. The high temperature thresholds of A. homolechis and A. sagrei may reflect their heat tolerances that would benefit these species to inhabit the open habitats.

  38. Candidate genes associated with color morphs of female-limited polymorphisms of the damselfly Ischnura senegalensis 査読有り

    Michihiko Takahashi, Yuma Takahashi, Masakado Kawata

    Heredity 122 1-12 2018年5月1日

    出版者・発行元:Nature Publishing Group

    DOI: 10.1038/s41437-018-0076-z  

    ISSN:1365-2540 0018-067X

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    Abstract: Many Odonata species exhibit female-limited polymorphisms, where one morph is similar to the conspecific male in body color and other traits (andromorph), whereas one or more other morphs differ from the male (gynomorphs). Here we investigated the differentially expressed transcripts (DETs) among males and two female morph groups (gynomorphs and andromorphs) using RNA-seq to identify candidate transcripts encoding female-limited polymorphisms in the damselfly Ischnura senegalensis. Seven DETs that had significantly different expression levels between males and gynomorphs, but not between males and andromorphs, were identified. The expression levels of four of these candidate genes, doublesex (dsx), black, ebony, and chaoptin (chp), were selected for further analysis using qRT-PCR. Sequence analysis of the dsx amplicons revealed that this gene produced at least three transcripts. Two short transcripts were mainly expressed in males and andromorphs, whereas the long transcript was specifically expressed in both morph female groups that is, the expression pattern of the dsx splice variants in andromorphs was an intermediate between that of males and gynomorphs. Because the dsx gene functions as a transcription factor that regulates the sex-specific expression of multiple genes, its splice variants in I. senegalensis may explain why the andromorph is female but exhibits some masculinized traits. Because we did not detect different coding sequences of the candidate genes among the different morphs, a diallelic genomic region controlling alternative splicing of dsx, thus determining female-limited polymorphism in I. senegalensis most likely lies in a non-coding region of the dsx gene or in a gene upstream of it.

  39. Isolation of uracil auxotroph mutants of coral symbiont alga for symbiosis studies. 国際誌 査読有り

    Yuu Ishii, Shinichiro Maruyama, Konomi Fujimura-Kamada, Natsumaro Kutsuna, Shunichi Takahashi, Masakado Kawata, Jun Minagawa

    Scientific reports 8 (1) 3237-3237 2018年2月19日

    DOI: 10.1038/s41598-018-21499-3  

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    Coral reef ecosystems rely on stable symbiotic relationship between the dinoflagellate Symbiodinium spp. and host cnidarian animals. The collapse of such symbiosis could cause coral 'bleaching' and subsequent host death. Despite huge interest on Symbiodinium, lack of mutant strains and readily available genetic tools have hampered molecular research. A major issue was the tolerance to marker antibiotics. Here, we isolated Symbiodinium mutants requiring uracil for growth, and hence, useful in transformation screening. We cultured Symbiodinium spp. cells in the presence of 5-fluoroorotic acid (5FOA), which inhibits the growth of cells expressing URA3 encoding orotidine-5'-monophosphate decarboxylase, and isolated cells that require uracil for growth. Sequence analyses and genetic complementation tests using yeast demonstrated that one of the mutant cell lines had a point mutation in URA3, resulting in a splicing error at an unusual exon-intron junction, and consequently, loss of enzyme activity. This mutant could maintain a symbiotic relationship with the model sea anemone Exaiptasia pallida only in sea water containing uracil. Results show that the URA3 mutant will be a useful tool for screening Symbiodinium transformants, both ex and in hospite, as survival in the absence of uracil is possible only upon successful introduction of URA3.

  40. Balanced genetic diversity improves population fitness 査読有り

    Yuma Takahashi, Ryoya Tanaka, Daisuke Yamamoto, Suzuki Noriyuki, Masakado Kawata

    Proceedings of the Royal Society B: Biological Sciences 285 20172045 2018年

  41. Inferring evolutionary responses of Anolis carolinensis introduced into the Ogasawara archipelago using whole genome sequence data 査読有り

    Satoshi Tamate, Watal M. Iwasaki, Kenneth L. Krysko, Brian J. Camposano, Hideaki Mori, Ryo Funayama, Keiko Nakayama, Takashi Makino, Masakado Kawata

    SCIENTIFIC REPORTS 7 18008 2017年12月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/s41598-017-17852-7  

    ISSN:2045-2322

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    Invaded species often can rapidly expand and establish in novel environments through adaptive evolution, resulting in devastating effects on native communities. However, it is unclear if genetic variation at whole-genomic levels is actually reduced in the introduced populations and which genetic changes have occurred responding to adaptation to new environments. In the 1960s, Anolis carolinensis was introduced onto one of the Ogasawara Islands, Japan, and subsequently expanded its range rapidly throughout two of the islands. Morphological comparison showed that lower hindlimb length in the introduced populations tended to be longer than those in its native Florida populations. Using re-sequenced whole genomic data, we estimated that the effective population size at the time of introduction was actually small (less than 50). We also inferred putative genomic regions subject to natural selection after this introduction event using SweeD and a method based on Tajima's D, pi and F-ST. Five candidate genes that were potentially subject to selection were estimated by both methods. The results suggest that there were standing variations that could potentially contribute to adaptation to nonnative environments despite the founder population being small.

  42. Utilization of photographs taken by citizens for estimating bumblebee distributions 査読有り

    Yukari Suzuki-Ohno, Jun Yokoyama, Tohru Nakashizuka, Masakado Kawata

    SCIENTIFIC REPORTS 7 11215 2017年9月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/s41598-017-10581-x  

    ISSN:2045-2322

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    Citizen science is a powerful tool for collecting large volumes of observational data on various species. These data are used to estimate distributions using environmental factors with Species Distribution Models (SDM). However, if citizens are inexperienced in recognizing organisms, they may report different species as the subject species. Here we show nation-wide bumblebee distributions using photographs taken by citizens in our project, and estimated distributions for six bumblebee species using land use, climate, and altitude data with SDM. We identified species from photographic images, and took their locations from GPS data of photographs or the text in e-mails. When we compared our data with conventional data for specimens in the Global Biodiversity Information Facility (GBIF), we found that the volume and the number of species were larger, and the bias of spatial range was lower, than those of GBIF. Our estimated distributions were more consistent with bumblebee distributions reported in previous studies than with those of GBIF. Our method was effective for collecting distribution data, and estimating distributions with SDM. The estimated SDM allows us to predict the previous and future species distributions, and to develop conservation policies taking account of future city planning and/ or global climate changes.

  43. HSF1 and HSF3 cooperatively regulate the heat shock response in lizards 査読有り

    Ryosuke Takii, Mitsuaki Fujimoto, Yuki Matsuura, Fangxu Wu, Namiko Oshibe, Eiichi Takaki, Arpit Katiyar, Hiroshi Akashi, Takashi Makino, Masakado Kawata, Akira Nakai

    PLOS ONE 12 (7) e0180776 2017年7月

    出版者・発行元:PUBLIC LIBRARY SCIENCE

    DOI: 10.1371/journal.pone.0180776  

    ISSN:1932-6203

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    Cells cope with temperature elevations, which cause protein misfolding, by expressing heat shock proteins (HSPs). This adaptive response is called the heat shock response (HSR), and it is regulated mainly by heat shock transcription factor (HSF). Among the four HSF family members in vertebrates, HSF1 is a master regulator of HSP expression during proteotoxic stress including heat shock in mammals, whereas HSF3 is required for the HSR in birds. To examine whether only one of the HSF family members possesses the potential to induce the HSR in vertebrate animals, we isolated cDNA clones encoding lizard and frog HSF genes. The reconstructed phylogenetic tree of vertebrate HSFs demonstrated that HSF3 in one species is unrelated with that in other species. We found that the DNA-binding activity of both HSF1 and HSF3 in lizard and frog cells was induced in response to heat shock. Unexpectedly, overexpression of lizard and frog HSF3 as well as HSF1 induced HSP70 expression in mouse cells during heat shock, indicating that the two factors have the potential to induce the HSR. Furthermore, knockdown of either HSF3 or HSF1 markedly reduced HSP70 induction in lizard cells and resistance to heat shock. These results demonstrated that HSF1 and HSF3 cooperatively regulate the HSR at least in lizards, and suggest complex mechanisms of the HSR in lizards as well as frogs.

  44. Factors restricting the range expansion of the invasive green anole Anolis carolinensis on Okinawa Island, Japan 査読有り

    Yukari Suzuki-Ohno, Kenjiro Morita, Nobuaki Nagata, Hideaki Mori, Shintaro Abe, Takashi Makino, Masakado Kawata

    ECOLOGY AND EVOLUTION 7 (12) 4357-4366 2017年6月

    出版者・発行元:WILEY

    DOI: 10.1002/ece3.3002  

    ISSN:2045-7758

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    The green anole Anolis carolinensis invaded the Ogasawara Islands in Japan, drove various native species to extinction, and its distribution expanded 14years after initial establishment. A. carolinensis invaded Okinawa Island, but it has not expanded its distribution in more than 25years, although its density is extremely high in the southern region. To determine whether A. carolinensis has the potential to expand its distribution on Okinawa Island, we performed phylogenetic analysis of mitochondrial ND2 DNA sequences to study the origin of A. carolinensis that invaded Okinawa Island. We further used a species distribution model (MaxEnt) based on the distribution of native populations in North America to identify ecologically suitable areas on Okinawa Island. Nucleotide sequence analysis shows that the invader A. carolinensis originated in the western part of the Gulf Coast and inland areas of the United States and that a portion of the anoles on Okinawa was not introduced via the Ogasawara Islands. The MaxEnt predictions indicate that most areas in Okinawa Island are suitable for A. carolinensis. Therefore, A.carolinensis may have the potential to expand its distribution in Okinawa Island. The predictions indicate that habitat suitability is high in areas of high annual mean temperature and urbanized areas. The values of precipitation in summer in the northern region of Okinawa Island were higher compared with those of North America, which reduced the habitat suitability in Okinawa Island. Adaptation to low temperatures, an increase in the mean temperature through global warming, and an increase in open environments through land development will likely expand the distribution of A. carolinensis in Okinawa Island. Therefore, we must continue to monitor the introduced populations and be alert to the possibility that city planning that increases open environments may cause their range to expand.

  45. Physiological conditions and genetic controls of phaeomelanin pigmentation in nestling barn swallows 査読有り

    Emi Arai, Masaru Hasegawa, Takashi Makino, Akihiko Hagino, Yusuke Sakai, Hajime Ohtsuki, Kazumasa Wakamatsu, Masakado Kawata

    BEHAVIORAL ECOLOGY 28 (3) 706-716 2017年5月

    出版者・発行元:OXFORD UNIV PRESS INC

    DOI: 10.1093/beheco/arx012  

    ISSN:1045-2249

    eISSN:1465-7279

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    Phaeomelanin is a common pigment that confers a reddish colour to animals. Since phaeomelanogenesis requires the sulfhydryl group from cysteine or glutathione (GSH), which is an important antioxidant, this pigmentation and the associated coloration may be an honest signal, whereby only high-quality individuals (e.g. with lower oxidative stress) are able to develop showy plumage. The present study tested the mechanisms underlying the honest signal hypothesis using nestling barn swallows, Hirundo rustica gutturalis, which exhibit phaeomelanic throat plumage patches. We examined the relationship between phaeomelanin pigmentation levels and physiological condition during trait development, and the expression of the phaeomelanin-related gene agouti-signalling protein (ASIP) and the GSH-related gene glutathione S-transferase (GST) in throat feather follicles. We found that during phaeomelanogenesis, heavier nestlings produced more pigmented feathers, indicating that nestlings with high phaeomelanin concentrations are in better condition. We also found that phaeomelanin concentration was negatively correlated with total GSH level, but not significantly related with measures of oxidative stress. Among the GST genes, GSTM3 exhibited the highest expression in the developing feathers during phaeomelanogenesis. The expression levels of ASIP were positively associated with the amount of phaeomelanin deposition and negatively associated with the expression of GSTM3, reducing the amount of GSH that was available as an antioxidant. These findings suggest that high-quality individuals produce high concentrations of phaeomelanin in their plumage without experiencing increased oxidative stress, despite phaeomelanin production, which is triggered by ASIP, potentially actively consuming the sulfhydryl group from GSH.

  46. The Effects of CpG Densities around Transcription Start Sites on Sex-Biased Gene Expression in Poecilia reticulata 査読有り

    Katsunori Tamagawa, Takashi Makino, Masakado Kawata

    GENOME BIOLOGY AND EVOLUTION 9 (5) 1204-1211 2017年5月

    出版者・発行元:OXFORD UNIV PRESS

    DOI: 10.1093/gbe/evx083  

    ISSN:1759-6653

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    As most genes are shared between females and males, DNA methylation is assumed to play a crucial role in sex-biased gene expression. DNA methylation exclusively occurs at CpG dinucleotides, and therefore, we would expect that CpG density around transcription start sites (TSSs) relate to sex-biased gene expression. Here we investigated the relationship between CpG densities around TSSs and the ratio of gene expression levels between sexes in the guppy (Poecilia reticulata), which displays remarkable sexual dimorphisms. We found that genes with sex-biased gene expression had different CpG densities downstream of TSSs compared with genes lacking sex-biased gene expression. Intriguingly, male-biased expression genes with intermediate CpG density downstream of TSSs exhibited greater differences in gene expression between sexes in the gonad and tail. Our findings suggested the possibility that CpGs around TSSs, especially in the downstream regions, play a crucial role in sex-biased gene expression through DNA methylation.

  47. Genetic variation and local differences in Pacific cod Gadus macrocephalus around Japan 査読有り

    A. Suda, N. Nagata, A. Sato, Y. Narimatsu, H. H. Nadiatul, M. Kawata

    JOURNAL OF FISH BIOLOGY 90 (1) 61-79 2017年1月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1111/jfb.13154  

    ISSN:0022-1112

    eISSN:1095-8649

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    The population structure of the Pacific cod Gadus macrocephalus was examined using 15 microsatellite loci and mitochondrial DNA (ND2 region). In total, 274 individuals were sampled from 16 locations around Japan to estimate the level of genetic differentiation and effective population size (N-e). Pairwise F-ST, analysis of molecular variance and Bayesian clustering analysis suggested the presence of two genetically distinct groups in waters around Japan, with a higher N-e value in the eastern group than in the western group. A possible factor that restricts gene flow between groups may be related to the water temperature differences in the south-western part of the Sea of Japan, where the Tsushima Warm Current flows around the area inhabited by the western group, which may limit migration between the west and east.

  48. Spatial Distribution of Flower Color Induced by Interspecific Sexual Interaction 査読有り

    Yuma Takahashi, Koh-ichi Takakura, Masakado Kawata

    PLOS ONE 11 (10) e0164381 2016年10月

    出版者・発行元:PUBLIC LIBRARY SCIENCE

    DOI: 10.1371/journal.pone.0164381  

    ISSN:1932-6203

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    Understanding the mechanisms shaping the spatiotemporal distribution of species has long been a central concern of ecology and evolutionary biology. Contemporary patterns of plant assemblies suggest that sexual interactions among species, i.e., reproductive interference, lead to the exclusive distributions of closely related species that share pollinators. However, the fitness consequences and the initial ecological/evolutionary responses to reproductive interference remain unclear in nature, since reproductive isolation or allopatric distribution has already been achieved in the natural community. In Japan, three species of blue-eyed grasses (Sisyrinchium) with incomplete reproductive isolation have recently colonized and occur sympatrically. Two of them are monomorphic with white flowers, whereas the other exhibits heritable color polymorphism (white and purple morphs). Here we investigated the effects of the presence of two monomorphic species on the distribution and reproductive success of color morphs. The frequency and reproductive success of white morphs decreased in area where monomorphic species were abundant, while those of purple morphs did not. The rate of hybridization between species was higher in white morphs than in the purple ones. Resource competition and habitat preference seemed not to contribute to the spatial distribution and reproductive success of two morphs. Our results supported that color-dependent reproductive interference determines the distribution of flower color polymorphism in a habitat, implying ecological sorting promoted by pollinator-mediated reproductive interference. Our study helps us to understand the evolution and spatial structure of flower color in a community.

  49. Spectral sensitivity of guppy visual pigments reconstituted in vitro to resolve association of opsins with cone cell types 査読有り

    Shoji Kawamura, Satoshi Kasagi, Daisuke Kasai, Ayumi Tezuka, Ayako Shoji, Akiyoshi Takahashi, Hiroo Imai, Masakado Kawata

    VISION RESEARCH 127 67-73 2016年10月

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.visres.2016.06.013  

    ISSN:0042-6989

    eISSN:1878-5646

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    The guppy (Poecilia reticulate) shows remarkable variation of photoreceptor cells in the retina, especially those sensitive to middle-to-long wavelengths of light. Microspectrophotometry (MSP) has revealed varying "green", "green-yellow" and "yellow" cone cells among guppies in Trinidad and Venezuela (Cumana). In the guppy genome, there are four "long-wave" opsin loci (LWS-1,-2,-3 and -4). Two LWS-1 alleles have potentially differing spectral sensitivity (LWS-1/180(Ser) and LWS-11180(Ala)). In addition, two "middle-wave" loci (RH2-1 and -2), two "short-wave" loci (SWS2-A and -B), and a single "ultraviolet" locus (SWS1) as well as a single "rhodopsin" locus (RH1) are present. However, the absorption spectra of these photopigments have not been measured directly and the association of cell types with these opsins remains speculative. In the present study, we reconstituted these opsin photopigments in vitro. The wavelengths of maximal absorbance (lambda(max)).) were 571 nm (LWS-//180(Ser)), 562 nm (LWS-1/180(Ala)), 519 nm (LWS-3), 516 nm (LWS-2), 516 nm (RH2-1), 476 nm (RH2-2), 438 nm (SWS2-A), 408 nm (SWS2-B), 353 nm (SWS1) and 503 nm (RH1). The lambda(max) of LWS-3 is much shorter than the value expected (560 nm) from the "five-sites" rule. The two LWS-1 alleles could explain difference of the reported MSP lambda(max) values for the yellow cone class between Trinidad and Cumana guppies. Absence of the short-wave-shifted LWS-3 and the green-yellow cone in the green swordtail supports the hypothesis that this cell class of the guppy co-expresses the LWS-1 and LWS-3. These results reveal the basis of variability in the guppy visual system and provide insight into the behavior and ecology of these tropical fishes. (C) 2016 The Authors. Published by Elsevier Ltd.

  50. Lack of genetic variation prevents adaptation at the geographic range margin in a damselfly 査読有り

    Yuma Takahashi, Yoshihisa Suyama, Yu Matsuki, Ryo Funayama, Keiko Nakayama, Masakado Kawata

    MOLECULAR ECOLOGY 25 (18) 4450-4460 2016年9月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1111/mec.13782  

    ISSN:0962-1083

    eISSN:1365-294X

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    What limits a species' distribution in the absence of physical barriers? Genetic load due to asymmetric gene flow and the absence of genetic variation due to lack of gene flow are hypothesized to constrain adaptation to novel environments in marginal populations, preventing range expansion. Here, we examined the genetic structure and geographic variation in morphological traits in two damselflies (Ischnura asiatica and I. senegalensis) along a latitudinal gradient in Japan, which is the distribution centre of I. asiatica and the northern limit of I. senegalensis. Genomewide genetic analyses found a loss of genetic diversity at the edge of distribution in I. senegalensis but consistently high diversity in I. asiatica. Gene flow was asymmetric in a south-north direction in both species. Although body size and wing loading showed decreasing latitudinal clines (smaller in north) in I. asiatica in Japan, increasing latitudinal clines (larger in north) in these phenotypic markers were observed in I. senegalensis, particularly near the northern boundary, which coincided well with the location where genetic diversity began a sharp decline. In ectothermic animals, increasing latitudinal cline in these traits was suggested to be established when they failed to adapt to thermal gradient. Therefore, our findings support the possibility that a lack of genetic variation rather than geneflow swamping is responsible for the constraint of adaptation at the margin of geographic distribution.

  51. Differentially expressed genes associated with adaptation to different thermal environments in three sympatric Cuban Anolis lizards 査読有り

    Hiroshi D. Akashi, Antonio Cadiz Diaz, Shuji Shigenobu, Takashi Makino, Masakado Kawata

    MOLECULAR ECOLOGY 25 (10) 2273-2285 2016年5月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1111/mec.13625  

    ISSN:0962-1083

    eISSN:1365-294X

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    How animals achieve evolutionary adaptation to different thermal environments is an important issue for evolutionary biology as well as for biodiversity conservation in the context of recent global warming. In Cuba, three sympatric species of Anolis lizards (Anolis allogus, A. homolechis and A. sagrei) inhabit different thermal microhabitats, thereby providing an excellent opportunity to examine how they have adapted to different environmental temperatures. Here, we performed RNA-seq on the brain, liver and skin tissues from these three species to analyse their transcriptional responses at two different temperatures. In total, we identified 400, 816 and 781 differentially expressed genes (DEGs) between the two temperatures in A. allogus, A. homolechis and A. sagrei, respectively. Only 62 of these DEGs were shared across the three species, indicating that global transcriptional responses have diverged among these species. Gene ontology (GO) analysis showed that large numbers of ribosomal protein genes were DEGs in the warm-adapted A. homolechis, suggesting that the upregulation of protein synthesis is an important physiological mechanism in the adaptation of this species to hotter environments. GO analysis also showed that GO terms associated with circadian regulation were enriched in all three species. A gene associated with circadian regulation, Nr1d1, was detected as a DEG with opposite expression patterns between the cool-adapted A. allogus and the hot-adapted A. sagrei. Because the environmental temperature fluctuates more widely in open habitats than in forests throughout the day, the circadian thermoregulation could also be important for adaptation to distinct thermal habitats.

  52. Effects of light environment during growth on the expression of cone opsin genes and behavioral spectral sensitivities in guppies (Poecilia reticulata) 査読有り

    Yusuke Sakai, Hajime Ohtsuki, Satoshi Kasagi, Shoji Kawamura, Masakado Kawata

    BMC EVOLUTIONARY BIOLOGY 16 106 2016年5月

    出版者・発行元:BIOMED CENTRAL LTD

    DOI: 10.1186/s12862-016-0679-z  

    ISSN:1471-2148

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    Background: The visual system is important for animals for mate choice, food acquisition, and predator avoidance. Animals possessing a visual system can sense particular wavelengths of light emanating from objects and their surroundings and perceive their environments by processing information contained in these visual perceptions of light. Visual perception in individuals varies with the absorption spectra of visual pigments and the expression levels of opsin genes, which may be altered according to the light environments. However, which light environments and the mechanism by which they change opsin expression profiles and whether these changes in opsin gene expression can affect light sensitivities are largely unknown. This study determined whether the light environment during growth induced plastic changes in opsin gene expression and behavioral sensitivity to particular wavelengths of light in guppies (Poecilia reticulata). Results: Individuals grown under orange light exhibited a higher expression of long wavelength-sensitive (LWS) opsin genes and a higher sensitivity to 600-nm light than those grown under green light. In addition, we confirmed that variations in the expression levels of LWS opsin genes were related to the behavioral sensitivities to long wavelengths of light. Conclusions: The light environment during the growth stage alters the expression levels of LWS opsin genes and behavioral sensitivities to long wavelengths of light in guppies. The plastically enhanced sensitivity to background light due to changes in opsin gene expression can enhance the detection and visibility of predators and foods, thereby affecting survival. Moreover, changes in sensitivities to orange light may lead to changes in the discrimination of orange/red colors of male guppies and might alter female preferences for male color patterns.

  53. Natural selection in a population of Drosophila melanogaster explained by changes in gene expression caused by sequence variation in core promoter regions 査読有り

    Mitsuhiko P. Sato, Takashi Makino, Masakado Kawata

    BMC EVOLUTIONARY BIOLOGY 16 35 2016年2月

    出版者・発行元:BIOMED CENTRAL LTD

    DOI: 10.1186/s12862-016-0606-3  

    ISSN:1471-2148

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    Background: Understanding the evolutionary forces that influence variation in gene regulatory regions in natural populations is an important challenge for evolutionary biology because natural selection for such variations could promote adaptive phenotypic evolution. Recently, whole-genome sequence analyses have identified regulatory regions subject to natural selection. However, these studies could not identify the relationship between sequence variation in the detected regions and change in gene expression levels. We analyzed sequence variations in core promoter regions, which are critical regions for gene regulation in higher eukaryotes, in a natural population of Drosophila melanogaster, and identified core promoter sequence variations associated with differences in gene expression levels subjected to natural selection. Results: Among the core promoter regions whose sequence variation could change transcription factor binding sites and explain differences in expression levels, three core promoter regions were detected as candidates associated with purifying selection or selective sweep and seven as candidates associated with balancing selection, excluding the possibility of linkage between these regions and core promoter regions. CHKov1, which confers resistance to the sigma virus and related insecticides, was identified as core promoter regions that has been subject to selective sweep, although it could not be denied that selection for variation in core promoter regions was due to linked single nucleotide polymorphisms in the regulatory region outside core promoter regions. Nucleotide changes in core promoter regions of CHKov1 caused the loss of two basal transcription factor binding sites and acquisition of one transcription factor binding site, resulting in decreased gene expression levels. Of nine core promoter regions regions associated with balancing selection, brat, and CG9044 are associated with neuromuscular junction development, and Nmda1 are associated with learning, behavioral plasticity, and memory. Diversity of neural and behavioral traits may have been maintained by balancing selection. Conclusions: Our results revealed the evolutionary process occurring by natural selection for differences in gene expression levels caused by sequence variation in core promoter regions in a natural population. The sequences of core promoter regions were diverse even within the population, possibly providing a source for natural selection.

  54. II-6. Evaluation for genetic diversity of marine fisheries resources after the tsunami caused by the 2011 off the pacific coast of Tohoku Earthquake 査読有り

    Minoru Ikeda, Yuki Minegishi, Daiki Ando, Manami Kanno, Akihiro Kijima, Shotaro Hirase, Sei-Ichi Okumura, Shunduke Moriyama, Kenta Adachi, Masakado Kawata, Ayako Suda, Sakiko Orui, Kiyotaka Takishita, Katsunori Fujikura

    Nippon Suisan Gakkaishi (Japanese Edition) 82 (2) 149 2016年

    出版者・発行元:Nihon Suisan Gakkai

    DOI: 10.2331/suisan.WA2247-15  

    ISSN:1349-998X 0021-5392

  55. Flower color polymorphism maintained by overdominant selection in Sisyrinchium sp. 査読有り

    Y. Takahashi, K. Takakura, M. Kawata

    Journal of Plant Research 128 (6) 933-939 2015年9月

    DOI: 10.1007/s10265  

  56. Developmental stages for the divergence of relative limb length between a twig and a trunk-ground Anolis lizard species 査読有り

    Hajime Wakasa, Antonio Cadiz, Lazaro M. Echenique-Diaz, Watal M. Iwasaki, Namiko Kamiyama, Yuki Nishimura, Hitoshi Yokoyama, Koji Tamura, Masakado Kawata

    JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 324 (5) 410-423 2015年7月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1002/jez.b.22627  

    ISSN:1552-5007

    eISSN:1552-5015

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    The divergent evolution of niche-related traits can facilitate adaptive radiation, yet identification of the genetic or molecular mechanisms underlying such trait changes remains a major challenge in evolutionary biology. Conducting a detailed morphological comparison along growth trajectories is a powerful method for observing the formation of differences in niche-related traits. Here, we focused on hindlimb length of Anolis lizards, differences in which are related to adaptation for use of different microhabitats. We measured the length of hindlimb skeletons in different ecomorphs of anole lizards (A. sagrei, a trunk-ground ecomorph with long hindlimbs, and A. angusticeps, a twig ecomorph with short hindlimbs) from early embryonic stages to adulthood, to determine which hindlimb elements mainly differentiate the species and the timing of the formation of these differences. With respect to the digit, differences between the species mainly occurred during the embryonic stages of interdigit reduction, when the cartilage of the distal phalanges was simultaneously forming. In addition, we compared the relative length of developing autopods in early embryonic stages using whole-mount in situ hybridization before the formation of the cartilaginous bones, and the results showed that the relative growth rate of the Hoxa11-negative distal region in A. sagrei was greater than that in A. angusticeps. Our results show that there are several important developmental stages for hindlimb length differentiation between A. angusticeps and A. sagrei, depending on which hindlimb element is considered. In particular, the species differences were largely due to variations in digit length, which arose at early embryonic stages. J. Exp. Zool. (Mol. Dev. Evol.) 324B: 410-423, 2015. (c) 2015 Wiley Periodicals, Inc.

  57. Evidence of introgressive hybridization between the morphologically divergent land snails Ainohelix and Ezohelix 査読有り

    Yuta Morii, Jun Yokoyama, Masakado Kawata, Angus Davison, Satoshi Chiba

    BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY 115 (1) 77-95 2015年5月

    出版者・発行元:OXFORD UNIV PRESS

    DOI: 10.1111/bij.12466  

    ISSN:0024-4066

    eISSN:1095-8312

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    Hybridization between different taxa is likely to take place when adaptive morphological differences evolve more rapidly than reproductive isolation. When studying the phylogenetic relationship between two land snails of different nominal genera, Ainohelix editha and Ezohelix gainesi, from Hokkaido, Japan, using nuclear internal transcribed spacer and mitochondrial 16S ribosomal DNA, we found a marked incongruence in the topology between nuclear and mitochondrial phylogenies. Furthermore, no clear association was found between shell morphology (which defines the taxonomy) and nuclear or mitochondrial trees and morphology of reproductive system. These patterns are most likely explained by historical introgressive hybridization between A.editha and E.gainesi. Because the shell morphologies of the two species are quite distinct, even when they coexist, the implication is that natural selection is able to maintain (or has recreated) distinct morphologies in the face of gene flow. Future studies may be able to reveal the regions of the genome that maintain the morphological differences between these species.(c) 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115, 77-95.

  58. Arms race between leaf-rolling weevils and parasitoids: diversification of weevil’s plant-manipulation behavior and its consequence. 査読有り

    Kobayashi C, Matsuo K, Watanab Ke, Nagata N, Suzuki-Ohno Y, Kawata M, Kato M

    Ecological Monographs 85 (2) 253-268 2015年5月

    出版者・発行元:None

    DOI: 10.1890/14-0280.1  

    ISSN:0012-9615

    eISSN:1557-7015

  59. Divergent selection for opsin gene variation in guppy (Poecilia reticulata) populations of Trinidad and Tobago 査読有り

    A. Tezuka, S. Kasagi, C. van Oosterhout, M. McMullan, W. M. Iwasaki, D. Kasai, M. Yamamichi, H. Innan, S. Kawamura, M. Kawata

    HEREDITY 113 (5) 381-389 2014年11月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/hdy.2014.35  

    ISSN:0018-067X

    eISSN:1365-2540

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    The guppy is known to exhibit remarkable interindividual variations in spectral sensitivity of middle to long wavelength-sensitive (M/LWS) cone photoreceptor cells. The guppy has four M/LWS-type opsin genes (LWS-1, LWS-2, LWS-3 and LWS-4) that are considered to be responsible for this sensory variation. However, the allelic variation of the opsin genes, particularly in terms of their absorption spectrum, has not been explored in wild populations. Thus, we examined nucleotide variations in the four M/LWS opsin genes as well as blue-sensitive SWS2-B and ultraviolet-sensitive SWS1 opsin genes for comparison and seven non-opsin nuclear loci as reference genes in 10 guppy populations from various light environments in Trinidad and Tobago. For the first time, we discovered a potential spectral variation (180 Ser/Ala) in LWS-1 that differed at an amino acid site known to affect the absorption spectra of opsins. Based on a coalescent simulation of the nucleotide variation of the reference genes, we showed that the interpopulation genetic differentiation of two opsin genes was significantly larger than the neutral expectation. Furthermore, this genetic differentiation was significantly related to differences in dissolved oxygen (DO) level, and it was not explained by the spatial distance between populations. The DO levels are correlated with eutrophication that possibly affects the color of aquatic environments. These results suggest that the population diversity of opsin genes is significantly driven by natural selection and that the guppy could adapt to various light environments through color vision changes.

  60. A worldwide survey of genome sequence variation provides insight into the evolutionary history of the honeybee Apis mellifera 査読有り

    Andreas Wallberg, Fan Han, Gustaf Wellhagen, Bjorn Dahle, Masakado Kawata, Nizar Haddad, Zila Luz Paulino Simoes, Mike H. Allsopp, Irfan Kandemir, Pilar De la Rua, Christian W. Pirk, Matthew T. Webster

    NATURE GENETICS 46 (10) 1081-1088 2014年10月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/ng.3077  

    ISSN:1061-4036

    eISSN:1546-1718

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    The honeybee Apis mellifera has major ecological and economic importance. We analyze patterns of genetic variation at 8.3 million SNPs, identified by sequencing 140 honeybee genomes from a worldwide sample of 14 populations at a combined total depth of 634x. These data provide insight into the evolutionary history and genetic basis of local adaptation in this species. We find evidence that population sizes have fluctuated greatly, mirroring historical fluctuations in climate, although contemporary populations have high genetic diversity, indicating the absence of domestication bottlenecks. Levels of genetic variation are strongly shaped by natural selection and are highly correlated with patterns of gene expression and DNA methylation. We identify genomic signatures of local adaptation, which are enriched in genes expressed in workers and in immune system and sperm motility related genes that might underlie geographic variation in reproduction, dispersal and disease resistance. This study provides a framework for future investigations into responses to pathogens and climate change in honeybees.

  61. Identification of hemiclonal reproduction in three species of Hexagrammos marine reef fishes 査読有り

    M. R. Kimura-Kawaguchi, M. Horita, S. Abe, K. Arai, M. Kawata, H. Munehara

    JOURNAL OF FISH BIOLOGY 85 (2) 189-209 2014年8月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1111/jfb.12414  

    ISSN:0022-1112

    eISSN:1095-8649

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    a Natural hybrids between the boreal species Hexagrammos octogrammus and two temperate species Hexagrammos agrammus and Hexagrammos otakii were observed frequently in southern Hokkaido, Japan. Previous studies revealed that H. octogrammus is a maternal ancestor of both hybrids; the hybrids are all fertile females and they frequently breed with paternal species. Although such rampant hybridization occurs, species boundaries have been maintained in the hybrid zone. Possible explanations for the absence of introgressions, despite the frequent backcrossing, might include clonal reproduction: parthenogenesis, gynogenesis and hybridogenesis. The natural hybrids produced haploid eggs that contained only the H. octogrammus genome (maternal ancestor) with discarded paternal genome and generated F-1-hybrid type offspring by fertilization with the haploid sperm of H. agrammus or H. otakii (paternal ancestor). This reproductive mode was found in an artificial backcross hybrid between the natural hybrid and a male of the paternal ancestor. These findings indicate that the natural hybrids adopt hybridogenesis with high possibility and produce successive generations through hybridogenesis by backcrossing with the paternal ancestor. These hybrids of Hexagrammos represent the first hybridogenetic system found from marine fishes that widely inhabit the North Pacific Ocean. In contrast with other hybridogenetic systems, these Hexagrammos hybrids coexist with all three ancestral species in the hybrid zone. The coexistence mechanism is also discussed. (C) 2014 The Fisheries Society of the British Isles

  62. Functional Morphology and Comparative Anatomy of Appendicular Musculature in Cuban Anolis Lizards with Different Locomotor Habits 査読有り

    Wataru Anzai, Ayano Omura, Antonio Cadiz Diaz, Masakado Kawata, Hideki Endo

    ZOOLOGICAL SCIENCE 31 (7) 454-463 2014年7月

    出版者・発行元:ZOOLOGICAL SOC JAPAN

    DOI: 10.2108/zs130062  

    ISSN:0289-0003

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    We examined the diversity of the musculoskeletal morphology in the limbs of Anolis lizards with different habitats and identified variations in functional and morphological adaptations to different ecologies or behaviors. Dissection and isolation of 40 muscles from the fore- and hindlimbs of five species of Anolis were performed, and the muscle mass and length of the moment arm were compared after body size effects were removed. Ecologically and behaviorally characteristic morphological differences were observed in several muscles. Well-developed hindlimb extensors were observed in ground-dwelling species, A. sagrei and A. bremeri, and were considered advantageous for running, whereas adept climber species possessed expanded femoral retractors for weight-bearing during climbing. Moreover, morphological variations were observed among arboreal species. Wider excursions of the forelimb joint characterized A. porcatus, presumably enabling branch-to-branch locomotion, while A. equestris and A. angusticeps possessed highly developed adductor muscles for grasping thick branches or twigs. These findings suggest divergent evolution of musculoskeletal characteristic in the limbs within the genus Anolis, with correlations observed among morphological traits, locomotor performance, and habitat uses.

  63. Contribution of Nonohnologous Duplicated Genes to High Habitat Variability in Mammals 査読有り

    Satoshi C. Tamate, Masakado Kawata, Takashi Makino

    MOLECULAR BIOLOGY AND EVOLUTION 31 (7) 1779-1786 2014年7月

    出版者・発行元:OXFORD UNIV PRESS

    DOI: 10.1093/molbev/msu128  

    ISSN:0737-4038

    eISSN:1537-1719

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    The mechanism by which genetic systems affect environmental adaptation is a focus of considerable attention in the fields of ecology, evolution, and conservation. However, the genomic characteristics that constrain adaptive evolution have remained unknown. A recent study showed that the proportion of duplicated genes in whole Drosophila genomes correlated with environmental variability within habitat, but it remains unclear whether the correlation is observed even in vertebrates whose genomes including a large number of duplicated genes generated by whole-genome duplication (WGD). Here, we focus on fully sequenced mammalian genomes that experienced WGD in early vertebrate lineages and show that the proportion of small-scale duplication (SSD) genes in the genome, but not that of WGD genes, is significantly correlated with habitat variability. Moreover, species with low habitat variability have a higher proportion of lost duplicated genes, particularly SSD genes, than those with high habitat variability. These results indicate that species that inhabit variable environments may maintain more SSD genes in their genomes and suggest that SSD genes are important for adapting to novel environments and surviving environmental changes. These insights may be applied to predicting invasive and endangered species.

  64. Evolution of increased phenotypic diversity enhances population performance by reducing sexual harassment in damselflies 査読有り

    Yuma Takahashi, Kotaro Kagawa, Erik I. Svensson, Masakado Kawata

    NATURE COMMUNICATIONS 5 4468 2014年7月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/ncomms5468  

    ISSN:2041-1723

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    The effect of evolutionary changes in traits and phenotypic/genetic diversity on ecological dynamics has received much theoretical attention; however, the mechanisms and ecological consequences are usually unknown. Female-limited colour polymorphism in damselflies is a counter-adaptation to male mating harassment, and thus, is expected to alter population dynamics through relaxing sexual conflict. Here we show the side effect of the evolution of female morph diversity on population performance (for example, population productivity and sustainability) in damselflies. Our theoretical model incorporating key features of the sexual interaction predicts that the evolution of increased phenotypic diversity will reduce overall fitness costs to females from sexual conflict, which in turn will increase productivity, density and stability of a population. Field data and mesocosm experiments support these model predictions. Our study suggests that increased phenotypic diversity can enhance population performance that can potentially reduce extinction rates and thereby influence macroevolutionary processes.

  65. Antagonistic selection factors induce a continuous population divergence in a polymorphism 査読有り

    Y. Takahashi, N. Nagata, M. Kawata

    HEREDITY 112 (4) 391-398 2014年4月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/hdy.2013.117  

    ISSN:0018-067X

    eISSN:1365-2540

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    Understanding the relative importance of selection and stochastic factors in population divergence of adaptive traits is a classical topic in evolutionary biology. However, it is difficult to separate these factors and detect the effects of selection when two or more contrasting selective factors are simultaneously acting on a single locus. In the damselfly Ischnura senegalensis, females exhibit color dimorphism and morph frequencies change geographically. We here evaluated the role of selection and stochastic factors in population divergence of morph frequencies by comparing the divergences in color locus and neutral loci. Comparisons between population pairwise FST for neutral loci and for the color locus did not detect any stochastic factors affecting color locus. Although comparison between population divergence in color and neutral loci using all populations detected only divergent selection, we detected two antagonistic selective factors acting on the color locus, that is, balancing and divergent selection, when considering geographical distance between populations. Our results suggest that a combination of two antagonistic selective factors, rather than stochastic factors, establishes the geographic cline in morph frequency in this system.

  66. Expression of the nos gene and firefly flashing: A test of the nitric-oxide-mediated flash control model 査読有り

    Hajime Ohtsuki, Jun Yokoyama, Nobuyoshi Ohba, Yoshihiro Ohmiya, Masakado Kawata

    JOURNAL OF INSECT SCIENCE 14 56 2014年4月

    出版者・発行元:OXFORD UNIV PRESS INC

    DOI: 10.1093/jis/14.1.56  

    ISSN:1536-2442

    eISSN:2250-2645

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    Fireflies (Coleoptera: Lampyridae) emit various types of light that differ among species and populations of the same species. Their lights are assumed to be biological properties that play important ecological and evolutionary roles. Some species in the Lampyridae emit periodic luminescence, the patterns of which are characterized by species-specific intervals. In previous work, it was predicted that the nitric oxide (NO) regulates the oxygen supply required for the bioluminescence reaction of fireflies. Here, the expression of the NO synthase (NOS) mRNA in some fireflies was examined to verify the predictive model of nitric-oxide-mediated flash control in these insects. The expression of the nos gene in the lantern organ was observed not only in nocturnal flashing species but also in diurnal non-flashing species. It was shown that the expression levels of nos were higher in the lantern of Luciola cruciata (Motschulsky) larvae, which that emits continuous light, than in other body parts, although expression in the lantern of the adults, who flash periodically, was not high. Furthermore, there was no significant difference in expression levels among adults of Luciola cruciata characterized by different flashing intervals. The data do not support the model of an NO-mediated flash control mechanism, during which oxygen becomes available for the luciferin-luciferase reaction through NO-mediated inhibition of mitochondrial respiration. It is also indicated that flash patterns do not co-vary with NOS production. However, high nos expression in the larval lantern suggests that NO may play a role in producing continuous light by functioning as a neurotransmitter signal for bioluminescence.

  67. Sex Chromosome Turnover Contributes to Genomic Divergence between Incipient Stickleback Species 査読有り

    Kohta Yoshida, Takashi Makino, Katsushi Yamaguchi, Shuji Shigenobu, Mitsuyasu Hasebe, Masakado Kawata, Manabu Kume, Seiichi Mori, Catherine L. Peichel, Atsushi Toyoda, Asao Fujiyama, Jun Kitano

    PLOS GENETICS 10 (3) e1004223 2014年3月

    出版者・発行元:PUBLIC LIBRARY SCIENCE

    DOI: 10.1371/journal.pgen.1004223  

    ISSN:1553-7390

    eISSN:1553-7404

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    Sex chromosomes turn over rapidly in some taxonomic groups, where closely related species have different sex chromosomes. Although there are many examples of sex chromosome turnover, we know little about the functional roles of sex chromosome turnover in phenotypic diversification and genomic evolution. The sympatric pair of Japanese threespine stickleback (Gasterosteus aculeatus) provides an excellent system to address these questions: the Japan Sea species has a neo-sex chromosome system resulting from a fusion between an ancestral Y chromosome and an autosome, while the sympatric Pacific Ocean species has a simple XY sex chromosome system. Furthermore, previous quantitative trait locus (QTL) mapping demonstrated that the Japan Sea neo-X chromosome contributes to phenotypic divergence and reproductive isolation between these sympatric species. To investigate the genomic basis for the accumulation of genes important for speciation on the neo-X chromosome, we conducted whole genome sequencing of males and females of both the Japan Sea and the Pacific Ocean species. No substantial degeneration has yet occurred on the neo-Y chromosome, but the nucleotide sequence of the neo-X and the neo-Y has started to diverge, particularly at regions near the fusion. The neo-sex chromosomes also harbor an excess of genes with sex-biased expression. Furthermore, genes on the neo-X chromosome showed higher non-synonymous substitution rates than autosomal genes in the Japan Sea lineage. Genomic regions of higher sequence divergence between species, genes with divergent expression between species, and QTL for inter-species phenotypic differences were found not only at the regions near the fusion site, but also at other regions along the neo-X chromosome. Neo-sex chromosomes can therefore accumulate substitutions causing species differences even in the absence of substantial neo-Y degeneration.

  68. Evolutionary history of maternal plant-manipulation and larval feeding behaviours in attelabidae (coleoptera; curculionoidea) and evolution of plant-basal weevil interaction 査読有り

    Chisato Kobayashi, Yudai Okuyama, Kazuhide Kawazoe, Masakado Kawata, Makoto Kato

    Evolutionary Biology: Genome Evolution, Speciation, Coevolution and Origin of Life 227-245 2014年1月1日

    出版者・発行元:Springer International Publishing

    DOI: 10.1007/978-3-319-07623-2_11  

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    Weevils are one of the dominant taxonomic groups in terrestrial ecosystem, diversifying to more than 60,000 described species. Although the most derived weevil group, Curculionidae, has adapted to and is utilising almost all parts of plant, basal groups show relatively limited larval feeding habits, such as pollen, seed, or fungus-infested wood feeders. Thus, it seems that ancestral larval infesting plant parts of weevils were restricted to N-rich, induced-defenseless, and temporal resources. Among the basal weevils, Attelabidae obtained such resources for their larvae by evolving unique maternal plant-manipulations: attelabid females manipulate specific young plant tissues of their host plants in a species-specific manner, e.g. cutting a shoot or a leaf, rolling a leaf, or constructing sophisticated wrapped leaf rolls, before and after oviposition presumably to secure the survivorship of eggs or larvae. Molecular phylogenetic analyses based on the nuclear 18S and 28S ribosomal DNA and the mitochondrial COI genes indicated that the maternal plant-cutting behaviour originated in a common ancestor of Attelabidae, but was subsequently lost in the several lineages. The monophyly was recovered for the subfamily Attelabinae with high support, but not for the subfamily Rhynchitinae. By employing maximum likelihood-based ancestral state reconstructions, the larval leaf-blade feeding was inferred to have evolved from the boring of cut shoots/petioles. Moreover, the maternal leaf-rolling behaviour might have originated independently in the Attelabinae, Byctiscini, and also in several Deporaini lineages. Since the sophisticated behaviour of Attelabinae, i.e. constructing wrapped leaf rolls, have originated only once and not been lost in the lineage, these complex and innovative behaviours may have contributed to the success of the lineage diversification.

  69. Sustaining ecosystem functions in a changing world: a call for an integrated approach 査読有り

    Hiroshi Tomimatsu, Takehiro Sasaki, Hiroko Kurokawa, Jon R. Bridle, Colin Fontaine, Jun Kitano, Daniel B. Stouffer, Mark Vellend, T. Martijn Bezemer, Tadashi Fukami, Elizabeth A. Hadly, Marcel G. A. van der Heijden, Masakado Kawata, Sonia Kefi, Nathan J. B. Kraft, Kevin S. McCann, Peter J. Mumby, Tohru Nakashizuka, Owen L. Petchey, Tamara N. Romanuk, Katharine N. Suding, Gaku Takimoto, Jotaro Urabe, Shigeo Yachi

    JOURNAL OF APPLIED ECOLOGY 50 (5) 1124-1130 2013年10月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1111/1365-2664.12116  

    ISSN:0021-8901

    eISSN:1365-2664

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    1. With ever-increasing human pressure on ecosystems, it is critically important to predict how ecosystem functions will respond to such human-induced perturbations. We define perturbations as either changes to abiotic environment (e.g. eutrophication, climate change) that indirectly affects biota, or direct changes to biota (e.g. species introductions). While two lines of research in ecology, biodiversity-ecosystem function (BDEF) and ecological resilience (ER) research, have addressed this issue, both fields of research have nontrivial shortcomings in their abilities to address a wide range of realistic scenarios. 2. We outline how an integrated research framework may foster a deeper understanding of the functional consequences of perturbations via simultaneous application of (i) process-based mechanistic predictions using trait-based approaches and (ii) detection of empirical patterns of functional changes along real perturbation gradients. In this context, the complexities of ecological interactions and evolutionary perspectives should be integrated into future research. 3. Synthesis and applications. Management of human-impacted ecosystems can be guided most directly by understanding the response of ecosystem functions to controllable perturbations. In particular, we need to characterize the form of a wide range of perturbation-function relationships and to draw connections between those patterns and the underlying ecological processes. We anticipate that the integrated perspectives will also be helpful for managers to derive practical implications for management from academic literature.

  70. Genome-wide deserts for copy number variation in vertebrates 査読有り

    Takashi Makino, Aoife McLysaght, Masakado Kawata

    NATURE COMMUNICATIONS 4 2283 2013年8月

    出版者・発行元:NATURE PUBLISHING GROUP

    DOI: 10.1038/ncomms3283  

    ISSN:2041-1723

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    Most copy number variations are neutral, but some are deleterious and associated with various human diseases. Copy number variations are distributed non-randomly in vertebrate genomes, and it was recently reported that ohnologs, which are duplicated genes derived from whole genome duplication, are refractory to copy number variations. However, it is unclear what genomic factors affect the deleterious effects of copy number variations and the biological significance of the biased genomic distribution of copy number variations remains poorly understood. Here we show that non-ohnologs neighbouring ohnologs are unlikely to have copy number variations, resulting in ohnolog-rich regions in vertebrate genomes being copy number variation deserts. Our results suggest that the genomic location of ohnologs is a determining factor in the retention of copy number variations and that the dosage-balanced ohnologs are likely to cause the deleterious effects of copy number variations in these regions. We propose that investigating copy number variation of genes in regions that are typically copy number variation deserts is an efficient means to find disease-related copy number variations.

  71. A comprehensive test for negative frequency-dependent selection 査読有り

    Yuma Takahashi, Masakado Kawata

    POPULATION ECOLOGY 55 (3) 499-509 2013年7月

    出版者・発行元:SPRINGER JAPAN KK

    DOI: 10.1007/s10144-013-0372-7  

    ISSN:1438-3896

    eISSN:1438-390X

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    Understanding the mechanisms that maintain genetic diversity within a population remains a primary challenge for evolutionary biology. Of the processes capable of maintaining variation, negative frequency-dependent selection (NFDS), under which rare phenotypes (or alleles) enjoy a high fitness advantage, is suggested to be the most powerful. However, few experimental studies have confirmed that this process operates in nature. Although a lot of suggestive evidence has separately been provided in various polymorphic systems, these are not enough to prove the existence of NFDS in each system. Here we present a general review of NFDS and point out some problems with previous works to develop reasonable alternative research strategies for testing NFDS. In the second half of this paper, we focused on NFDS in the common bluetail damselfly, Ischnura senegalensis, that shows female-limited genetic polymorphism. We show (1) the proximate causal mechanisms of the frequency-dependent process, (2) frequency-dependent inter-morph interaction, (3) rare morph advantage and (4) morph frequency oscillations in a natural population. These results provide unequivocal empirical support for NFDS in a natural system.

  72. Alternative trait combinations and secondary resource partitioning in sexually selected color polymorphism 査読有り

    Yuma Takahashi, Masakado Kawata

    ECOLOGY AND EVOLUTION 3 (7) 2038-2046 2013年7月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1002/ece3.610  

    ISSN:2045-7758

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    &lt;title content-type="main"&gt;Abstract Resource partitioning within a species, trophic polymorphism is hypothesized to evolve by disruptive selection when intraspecific competition for certain resources is severe. However, in this study, we reported the secondary partitioning of oviposition resources without resource competition in the damselfly Ischnura senegalensis. In this species, females show color polymorphism that has been evolved as counteradaptation against sexual conflict. One of the female morphs is a blue-green (andromorph, male-like morph), whereas the other morph is brown (gynomorph). These female morphs showed alternative preferences for oviposition resources (plant tissues); andromorphs used fresh (greenish) plant tissues, whereas gynomorphs used decaying (brownish) plants tissues, suggesting that they chose oviposition resources on which they are more cryptic. In addition, the two-color morphs had different egg morphologies. Andromorphs have smaller and more elongated eggs, which seemed to adapt to hard substrates compared with those of gynomorphs. The resource partitioning in this species is achieved by morphological and behavioral differences between the color morphs that allow them to effectively exploit different resources. Resource partitioning in this system may be a by-product of phenotypic integration with body color that has been sexually selected, suggesting an overlooked mechanism of the evolution of resource partitioning. Finally, we discuss the evolutionary and ecological consequences of such resource partitioning.

  73. Relative importance of habitat use, range expansion, and speciation in local species diversity of Anolis lizards in Cuba 査読有り

    Antonio Cadiz, Nobuaki Nagata, Masatoshi Katabuchi, Luis M. Diaz, Lazaro M. Echenique-Diaz, Hiroshi D. Akashi, Takashi Makino, Masakado Kawata

    ECOSPHERE 4 (7) art78 2013年7月

    出版者・発行元:ECOLOGICAL SOC AMER

    DOI: 10.1890/ES12-00383.1  

    ISSN:2150-8925

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    Variations in species richness of local assemblages may be explained by local ecological processes or large-scale evolutionary and biogeographical processes. In Anolis lizards, species with different ecomorphs can coexist by occupying different niches. In addition, several species with the same ecomorph (e. g., trunk-ground) can coexist, and the number of trunk-ground anole species varies among local species assemblages. In this study, we assessed the importance of ecological interactions, number of speciation events, and range expansion for local and regional species diversity of these lizards. We examined the species richness and thermal microhabitat partitioning (considered to be a measure of ecological interaction) of 12 trunk-ground anole species in 11 local assemblages in Cuba. The results indicated that the phylogenetic structure of trunk-ground anole lizard assemblages was random. However, there was an overdispersion of preferences for thermal microhabitat use, which indicates that differences in microhabitat use are likely to occur within assemblages. We suggest that the number of speciation events within regions and the number of sympatrically coexisting species increases species richness at the local level. Migration appeared to be limited, leading to the range expansion of only three species with different thermal requirements. The thermal niches of species were conserved within Anolis allogus clade, whereas species within the Anolis homolechis and Anolis sagrei clades tended to change their thermal niches. Our results suggest that the species composition and richness in local assemblages could be explained by evolutionary history (the number of speciation events and limits to range expansion) and ecological processes (habitat partitioning). Of the ecological factors, the number of thermal (microhabitat use) and structural niches (e.g., vegetation) could limit the potential number of coexisting species within a local assemblage.

  74. Genetic and environmental factors affecting cryptic variations in gene regulatory networks 査読有り

    Watal M. Iwasaki, Masaki E. Tsuda, Masakado Kawata

    BMC EVOLUTIONARY BIOLOGY 13 91 2013年4月

    出版者・発行元:BIOMED CENTRAL LTD

    DOI: 10.1186/1471-2148-13-91  

    ISSN:1471-2148

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    Background: Cryptic genetic variation (CGV) is considered to facilitate phenotypic evolution by producing visible variations in response to changes in the internal and/or external environment. Several mechanisms enabling the accumulation and release of CGVs have been proposed. In this study, we focused on gene regulatory networks (GRNs) as an important mechanism for producing CGVs, and examined how interactions between GRNs and the environment influence the number of CGVs by using individual-based simulations. Results: Populations of GRNs were allowed to evolve under various stabilizing selections, and we then measured the number of genetic and phenotypic variations that had arisen. Our results showed that CGVs were not depleted irrespective of the strength of the stabilizing selection for each phenotype, whereas the visible fraction of genetic variation in a population decreased with increasing strength of selection. On the other hand, increasing the number of different environments that individuals encountered within their lifetime (i.e., entailing plastic responses to multiple environments) suppressed the accumulation of CGVs, whereas the GRNs with more genes and interactions were favored in such heterogeneous environments. Conclusions: Given the findings that the number of CGVs in a population was largely determined by the size (order) of GRNs, we propose that expansion of GRNs and adaptation to novel environments are mutually facilitating and sustainable sources of evolvability and hence the origins of biological diversity and complexity.

  75. Habitat Variability Correlates with Duplicate Content of Drosophila Genomes 査読有り

    Takashi Makino, Masakado Kawata

    MOLECULAR BIOLOGY AND EVOLUTION 29 (10) 3169-3179 2012年10月

    出版者・発行元:OXFORD UNIV PRESS

    DOI: 10.1093/molbev/mss133  

    ISSN:0737-4038

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    The factors limiting the habitat range of species are crucial in understanding their biodiversity and response to environmental change. Yet the genetic and genomic architectures that produce genetic variation to enable environmental adaptation have remained poorly understood. Here we show that the proportion of duplicated genes (P-D) in the whole genomes of fully sequenced Drosophila species is significantly correlated with environmental variability within the habitats measured by the climatic envelope and habitat diversity. Furthermore, species with a low P-D tend to lose the duplicated genes owing to their faster evolution. These results indicate that the rapid relaxation of functional constraints on duplicated genes resulted in a low P-D for species with lower habitat diversity, and suggest that the maintenance of duplicated genes gives organisms an ecological advantage during evolution. We therefore propose that the P-D in a genome is related to adaptation to environmental variation.

  76. Evolution of Vertebrate Tissues Driven by Differential Modes of Gene Duplication 査読有り

    Satake Masanobu, Kawata Masakado, McLysaght Aoife, Makino Takashi

    DNA RESEARCH 19 (4) 305-316 2012年8月

    出版者・発行元:OXFORD UNIV PRESS

    DOI: 10.1093/dnares/dss012  

    ISSN:1340-2838

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    On this study, we investigated the evolution of vertebrate tissues by examining the potential association among gene expression, duplication, and base substitution patterns. On particular, we compared whole-genome duplication (WGD) with small-scale duplication (SSD), as well as tissue restricted with ubiquitously expressed genes. All patterns were also analysed in the light of gene evolutionary rates. Among those genes characterized by rapid evolution and expressed in a restricted range of tissues, SSD was represented in a larger proportion than WGD. Conversely, genes with ubiquitous expression were associated with slower evolutionary rates and a larger proportion of WGD. The results also show that evolutionary rates were faster in genes expressed in endodermal tissues and slower in ectodermal genes. Accordingly, the proportion of the SSD and WGD genes was highest in the endoderm and ectoderm, respectively. Therefore, quickly evolving SSD genes might have contributed to the faster evolution of endodermal tissues, whereas the comparatively slowly evolving WGD genes might have functioned to maintain the basic characteristics of ectodermal tissues. Mesenchymal tissues occupied an intermediate position in this regard, whereas the patterns observed for haemocytes were unique. Rapid tissue evolution could be related to a specific gene duplication mode (SSD) and faster molecular evolution in response to exposure to the external environment. These findings reveal general patterns underlying the evolution of tissues and their corresponding genes.

  77. Shifts in morphology and diet of non-native sticklebacks introduced into Japanese crater lakes 査読有り

    Tatsuya Adachi, Asano Ishikawa, Seiichi Mori, Wataru Makino, Manabu Kume, Masakado Kawata, Jun Kitano

    ECOLOGY AND EVOLUTION 2 (6) 1083-1098 2012年6月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1002/ece3.234  

    ISSN:2045-7758

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    An increasing number of exotic animals are causing ecological problems. Therefore, for better ecosystem management, it is important to understand how exotic species colonize and adapt to novel environments. The threespine sticklebacks (Gasterosteus aculeatus) can be a good vertebrate model system to explore the ecological and genetic mechanisms of adaptation not only in natural populations, but also in non-native populations. Although morphological changes have been documented in several introduced populations of stickleback, little is known about the dietary changes during colonization into novel environments. Here, we investigated the morphological and dietary changes of exotic threespine stickleback populations introduced into three Japanese crater lakes (Lake Towada, Lake Kussharo, and Lake Shikotsu). Sticklebacks were introduced into the crater lakes likely along with salmonids transplanted for aquaculture. The stickleback population in Lake Kussharo had multiple mitochondrial haplotypes and had larger phenotypic variances than other crater lake stickleback populations that had only one mitochondrial haplotype. Compilation of historical data on the morphology and stomach contents of the Lake Towada stickleback population showed that substantial shifts in body size and stomach contents occurred after colonization. Some of these changes may be related to an outbreak of the Schistocephalus parasite. These results suggest that sticklebacks can change their morphology and trophic ecology when they colonize novel environments. Therefore, extreme care should be taken when salmonids are transported between watersheds for aquaculture and that long-term monitoring of exotic species is essential for ecosystem management. In addition, further genetic studies on phenotypic changes in crater lake sticklebacks would help elucidate the genetic mechanisms underlying the adaptation of exotic fishes to novel environments.

  78. Optimal feeding under stoichiometric constraints: a model of compensatory feeding with functional response 査読有り

    Yukari Suzuki-Ohno, Masakado Kawata, Jotaro Urabe

    OIKOS 121 (4) 569-578 2012年4月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1111/j.1600-0706.2011.19320.x  

    ISSN:0030-1299

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    When the nutrient content of food is limited, herbivores often increase their feeding rates. Such an increase in the feeding rate is called compensatory feeding. Although it has a number of implications for herbivore population and plantforager dynamics, the compensatory feeding is not yet functionally formulated especially in relation with ecological stoichiometry. Therefore, we constructed a simple mathematical model by incorporating the optimal feeding rate into the type II functional response to maximize a forager's growth rate under constraints of carbon or nutritionally important element like phosphorus (P). We used the planktonic herbivore Daphnia as a model herbivore. The model revealed that the optimal feeding rate increased by using excess carbon when relative P content of food was less than a certain level, which is known as the threshold elemental ratio. This level changed with the change of food abundance. It also showed that whether or not foragers should exhibit compensatory feeding depends on their stoichiometric characteristics and digestive traits, and also on the assimilability of a given food. These findings are helpful to test the feeding conditions under which compensatory feeding is advantageous for a given animal. Our model can be easily incorporated into forager population dynamics and prey-consumer interaction models because the optimal feeding rate can be analytically given.

  79. Comprehensive Primer Design for Analysis of Population Genetics in Non-Sequenced Organisms 査読有り

    Ayumi Tezuka, Noe Matsushima, Yoriko Nemoto, Hiroshi D. Akashi, Masakado Kawata, Takashi Makino

    PLOS ONE 7 (2) e32314 2012年2月

    出版者・発行元:PUBLIC LIBRARY SCIENCE

    DOI: 10.1371/journal.pone.0032314  

    ISSN:1932-6203

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    Nuclear sequence markers are useful tool for the study of the history of populations and adaptation. However, it is not easy to obtain multiple nuclear primers for organisms with poor or no genomic sequence information. Here we used the genomes of organisms that have been fully sequenced to design comprehensive sets of primers to amplify polymorphic genomic fragments of multiple nuclear genes in non-sequenced organisms. First, we identified a large number of candidate polymorphic regions that were flanked on each side by conserved regions in the reference genomes. We then designed primers based on these conserved sequences and examined whether the primers could be used to amplify sequences in target species, montane brown frog (Rana ornativentris), anole lizard (Anolis sagrei), guppy (Poecilia reticulata), and fruit fly (Drosophila melanogaster), for population genetic analysis. We successfully obtained polymorphic markers for all target species studied. In addition, we found that sequence identities of the regions between the primer sites in the reference genomes affected the experimental success of DNA amplification and identification of polymorphic loci in the target genomes, and that exonic primers had a higher success rate than intronic primers in amplifying readable sequences. We conclude that this comparative genomic approach is a time-and cost-effective way to obtain polymorphic markers for non-sequenced organisms, and that it will contribute to the further development of evolutionary ecology and population genetics for non-sequenced organisms, aiding in the understanding of the genetic basis of adaptation.

  80. Divergence in Sex Steroid Hormone Signaling between Sympatric Species of Japanese Threespine Stickleback 査読有り

    Jun Kitano, Yui Kawagishi, Seiichi Mori, Catherine L. Peichel, Takashi Makino, Masakado Kawata, Makoto Kusakabe

    PLOS ONE 6 (12) e29253 2011年12月

    出版者・発行元:PUBLIC LIBRARY SCIENCE

    DOI: 10.1371/journal.pone.0029253  

    ISSN:1932-6203

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    Sex steroids mediate the expression of sexually dimorphic or sex-specific traits that are important both for mate choice within species and for behavioral isolation between species. We investigated divergence in sex steroid signaling between two sympatric species of threespine stickleback (Gasterosteus aculeatus): the Japan Sea form and the Pacific Ocean form. These sympatric forms diverge in both male display traits and female mate choice behaviors, which together contribute to asymmetric behavioral isolation in sympatry. Here, we found that plasma levels of testosterone and 17 beta-estradiol differed between spawning females of the two sympatric forms. Transcript levels of follicle-stimulating hormone-beta (FSH beta) gene were also higher in the pituitary gland of spawning Japan Sea females than in the pituitary gland of spawning Pacific Ocean females. By contrast, none of the sex steroids examined were significantly different between nesting males of the two forms. However, combining the plasma sex steroid data with testis transcriptome data suggested that the efficiency of the conversion of testosterone into 11-ketotestosterone has likely diverged between forms. Within forms, plasma testosterone levels in males were significantly correlated with male body size, a trait important for female mate choice in the two sympatric species. These results demonstrate that substantial divergence in sex steroid signaling can occur between incipient sympatric species. We suggest that investigation of the genetic and ecological mechanisms underlying divergence in hormonal signaling between incipient sympatric species will provide a better understanding of the mechanisms of speciation in animals.

  81. The long-term consequences of hybridization between the two Daphnia species, D. galeata and D. dentifera, in mature habitats 査読有り

    Seiji Ishida, Akiko Takahashi, Noe Matsushima, Jun Yokoyama, Wataru Makino, Jotaro Urabe, Masakado Kawata

    BMC EVOLUTIONARY BIOLOGY 11 209 2011年7月

    出版者・発行元:BIOMED CENTRAL LTD

    DOI: 10.1186/1471-2148-11-209  

    ISSN:1471-2148

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    Background: Ecological specializations such as antipredator defense can reinforce morphological and distributional divergence within hybridizing species. Two hybridizing species of Daphnia (D. galeata and D. dentifera) are distributed in both Japan and North America; however, these populations have a longer history in Japan than in North America due to the differing impact of the last glaciation on these two regions. We tested the hypothesis that this longer coexistence in Japan would lead to extensive genetic admixture in nuclear and mitochondrial DNA whilst the distinct morphological traits and distributional patterns would be maintained. Results: The high level of correspondence among morphological traits, distribution, and mitochondrial and nuclear DNA types for the specimens with D. dentifera mtDNA indicated that the species distinction has been maintained. However, a discordance between mtDNA and nuclear ITS-1 types was observed for most specimens that had D. galeata mtDNA, consistent with the pattern seen between the two species in North America. This observation suggests nuclear introgression from D. dentifera into D. galeata without mitochondrial introgression. Conclusions: The separation of morphological traits and distribution ranges of the two hybridizing species in Japan, as well as in North America, has been maintained, despite large differences in climatic and geographical histories of these two regions. Variations in environmental factors, such as predation pressure, might affect maintenance of the distribution, although the further studies are needed to confirm this.

  82. Phenotypic and genetic differences in a perennial herb across a natural gradient of CO2 concentration 査読有り

    Ito Nakamura, Yusuke Onoda, Noe Matsushima, Jun Yokoyama, Masakado Kawata, Kouki Hikosaka

    OECOLOGIA 165 (3) 809-818 2011年3月

    出版者・発行元:SPRINGER

    DOI: 10.1007/s00442-010-1900-1  

    ISSN:0029-8549

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    The atmospheric CO2 concentration [CO2] has been increasing markedly since the industrial revolution and is predicted to reach 500-1,000 mu mol mol(-1) by the end of this century. Although the short-term and acclimatory responses to elevated [CO2] have been well studied, much less is understood about evolutionary responses to high [CO2]. We studied phenotypic and genetic differences in Plantago asiatica populations around a natural CO2 spring, where [CO2] has been consistently high over an evolutionary time scale. Our common-garden experiment revealed that plants transferred from habitats with higher [CO2] had higher relative growth rates, greater leaf to root ratios, lower photosynthetic rates, and lower stomatal conductance. The habitat-dependent differences were partly heritable because a similar trend of leaf to root ratio was found among their offsprings. Genetic analyses indicated that selfing or biparental inbreeding might promote local adaptation in areas with high [CO2] despite substantial gene flow across the [CO2] gradient. These results indicate that phenotypic and genetic differences have occurred between high and normal [CO2] populations.

  83. Effects of evolutionary changes in prey use on the relationship between food web complexity and stability 査読有り

    Wakako Yamaguchi, Michio Kondoh, Masakado Kawata

    POPULATION ECOLOGY 53 (1) 59-72 2011年1月

    出版者・発行元:SPRINGER TOKYO

    DOI: 10.1007/s10144-010-0212-y  

    ISSN:1438-3896

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    The relationship between food web complexity and stability has been the subject of a long-standing debate in ecology. Although rapid changes in the food web structure through adaptive foraging behavior can confer stability to complex food webs, as reported by Kondoh (Science 299:1388-1391, 2003), the exact mechanisms behind this adaptation have not been specified in previous studies; thus, the applicability of such predictions to real ecosystems remains unclear. One mechanism of adaptive foraging is evolutionary change in genetically determined prey use. We constructed individual-based models of evolution of prey use by predators assuming explicit population genetics processes, and examined how this evolution affects the stability (i.e., the proportion of species that persist) of the food web and whether the complexity of the food web increased the stability of the prey-predator system. The analysis showed that the stability of food webs decreased with increasing complexity regardless of evolution of prey use by predators. The effects of evolution on stability differed depending on the assumptions made regarding genetic control of prey use. The probabilities of species extinctions were associated with the establishment or loss of trophic interactions via evolution of the predator, indicating a clear link between structural changes in the food web and community stability.

  84. The MC1R gene in the guppy (Poecilia reticulata): Genotypic and phenotypic polymorphisms 査読有り

    Ayumi Tezuka, Hiroaki Yamamoto, Jun Yokoyama, Cock Van Oosterhout, Masakado Kawata

    BMC Research Notes 4 31 2011年

    DOI: 10.1186/1756-0500-4-31  

    ISSN:1756-0500

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    Background: The guppy (Poecilia reticulata) is an important model organism for studying sexual selection male guppies have complex and conspicuous pigmentation, and female guppies exhibit preferences for males with specific color spots. Understanding the genetic basis underlying pigmentation variation in the guppy is important for exploring the factors causing the maintenance of color polymorphism in wild populations. Findings. We focused on the melanic black pigmentation of guppies, and examined genetic variations in the melanocortin 1 receptor (MC1R) gene because variation in this gene is known to contribute to polymorphism of melanin pigmentation in several animal species. The complete coding sequence of the guppy MC1R gene was determined, and two different MC1R alleles (963 and 969 bp) were found in wild populations. Ornamental strain guppies with a 963-bp MC1R tended to show less black pigmentation than those with a 969-bp MC1R, although the association between MC1R genotype and black pigmentation disappeared in the F2offspring. Conclusions: The guppy MC1R gene showed variation in the five wild Trinidadian populations we examined, and these populations also differed in terms of allele frequencies. We identified a significant association between black pigmentation and MC1R genotype in fish obtained from aquarium shops. However, the results from F2families suggest that there are other genes that modify the effects of the MC1R gene. © 2011 Tezuka et al licensee BioMed Central Ltd.

  85. Evolution of Gene Regulatory Networks by Fluctuating Selection and Intrinsic Constraints 査読有り

    Masaki E. Tsuda, Masakado Kawata

    PLOS COMPUTATIONAL BIOLOGY 6 (8) e1000873 2010年8月

    出版者・発行元:PUBLIC LIBRARY SCIENCE

    DOI: 10.1371/journal.pcbi.1000873  

    ISSN:1553-734X

    eISSN:1553-7358

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    Various characteristics of complex gene regulatory networks (GRNs) have been discovered during the last decade, e. g., redundancy, exponential indegree distributions, scale-free outdegree distributions, mutational robustness, and evolvability. Although progress has been made in this field, it is not well understood whether these characteristics are the direct products of selection or those of other evolutionary forces such as mutational biases and biophysical constraints. To elucidate the causal factors that promoted the evolution of complex GRNs, we examined the effect of fluctuating environmental selection and some intrinsic constraining factors on GRN evolution by using an individual-based model. We found that the evolution of complex GRNs is remarkably promoted by fixation of beneficial gene duplications under unpredictably fluctuating environmental conditions and that some internal factors inherent in organisms, such as mutational bias, gene expression costs, and constraints on expression dynamics, are also important for the evolution of GRNs. The results indicate that various biological properties observed in GRNs could evolve as a result of not only adaptation to unpredictable environmental changes but also non-adaptive processes owing to the properties of the organisms themselves. Our study emphasizes that evolutionary models considering such intrinsic constraining factors should be used as null models to analyze the effect of selection on GRN evolution.

  86. Why is adaptation prevented at ecological margins? New insights from individual-based simulations 査読有り

    Jon R. Bridle, Jitka Polechova, Masakado Kawata, Roger K. Butlin

    ECOLOGY LETTERS 13 (4) 485-494 2010年4月

    出版者・発行元:WILEY

    DOI: 10.1111/j.1461-0248.2010.01442.x  

    ISSN:1461-023X

    eISSN:1461-0248

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    P&gt;All species are restricted in their distribution. Currently, ecological models can only explain such limits if patches vary in quality, leading to asymmetrical dispersal, or if genetic variation is too low at the margins for adaptation. However, population genetic models suggest that the increase in genetic variance resulting from dispersal should allow adaptation to almost any ecological gradient. Clearly therefore, these models miss something that prevents evolution in natural populations. We developed an individual-based simulation to explore stochastic effects in these models. At high carrying capacities, our simulations largely agree with deterministic predictions. However, when carrying capacity is low, the population fails to establish for a wide range of parameter values where adaptation was expected from previous models. Stochastic or transient effects appear critical around the boundaries in parameter space between simulation behaviours. Dispersal, gradient steepness, and population density emerge as key factors determining adaptation on an ecological gradient.

  87. The effects of the evolution of stoichiometry-related traits on population dynamics in plankton communities 査読有り

    Akiko N. Mizuno, Masakado Kawata

    JOURNAL OF THEORETICAL BIOLOGY 259 (2) 209-218 2009年7月

    出版者・発行元:ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.jtbi.2009.02.025  

    ISSN:0022-5193

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    Both ecological stoichiometry and the evolution of traits for energetic interactions such as prey protection and predatory efficiency are considered to be important aspects affecting population dynamics. However, no attempt has been made to examine the effect of the evolution of traits relating to stoichiometry. This study first examined the effects of the evolution of nutrient utilization traits (i.e., the minimum nutrient content of prey, the maximum nutrient uptake affinity of prey and the nutrient contents of predators) on population dynamics in a plankton community. When the evolution of these traits was assumed, the range of the nutrient loading conditions where the system became unstable was smaller than when the evolution was not assumed, but the range of the conditions for zooplankton extinction became larger. Furthermore, when the trade-offs (i.e. genetic correlation between the traits) were assumed, the system rarely became extinct and the range of the nutrient loading conditions where the system became stable became larger through evolution. Stable dynamics were caused by increasing uptake affinity through evolution, and zooplankton extinction was caused by decreasing the minimum content of limiting nutrients. Thus, our results suggest that the evolution of traits relating to stoichiometry can affect the dynamics of the systems. and the outcomes the dynamics change greatly depend on which traits can evolve. (C) 2009 Elsevier Ltd. All rights reserved.

  88. Genetic structure of island populations of the endangered bat Hipposideros turpis turpis: implications for conservation 査読有り

    Lazaro Miguel Echenique-Diaz, Jun Yokoyama, Osamu Takahashi, Masakado Kawata

    POPULATION ECOLOGY 51 (1) 153-160 2009年1月

    出版者・発行元:SPRINGER TOKYO

    DOI: 10.1007/s10144-008-0111-7  

    ISSN:1438-3896

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    Efforts for the conservation of the endangered bat species Hipposideros turpis turpis in southern Japan are hampered by a lack of information about its biology and natural history and by the increasing effect of human activities. In an attempt to address some of the conservation challenges faced by this species, we studied the genetic structure and dispersal of intra- and interisland populations using six species-specific microsatellite markers. In particular, we sought to establish the relationship between island populations and to define effective management units for conservation. Pairwise co-ancestry index (F (ST)) analysis, analysis of molecular variance, and Bayesian clustering suggested the presence of significant genetic differentiation between islands but little differentiation within them. The small Yonaguni Island population appeared to be not only geographically isolated, but also genetically isolated. This population is at the greatest risk of extinction, considering its size and low genetic variation. The larger populations on Iriomote and Ishigaki Islands are genetically related to each other to a greater degree and exhibit higher genetic variation than the Yonaguni Island population. This suggests that these two island populations should be included in a single management unit, while bats from Yonaguni Island should be managed independently and given higher priority for conservation. Actions such as defining vegetation corridors between colonies, as well as building gates at the entrance of the largest known colony, should be included in the conservation agenda of this still poorly known species.

  89. Size-dependent foraging gene expression and behavioral caste differentiation in Bombus ignitus 査読有り

    Yosuke Kodaira, Hajime Ohtsuki, Jun Yokoyama, Masakado Kawata

    BMC Research Notes 2 2009年

    DOI: 10.1186/1756-0500-2-184  

    ISSN:1756-0500

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    Background. In eusocial hymenopteran insects, foraging genes, members of the cGMP-dependent protein kinase family, are considered to contribute to division of labor through behavioral caste differentiation. However, the relationship between foraging gene expression and behavioral caste in honeybees is opposite to that observed in ants and wasps. In the previously examined eusocial Hymenoptera, workers behave as foragers or nurses depending on age. We reasoned that examination of a different system of behavioral caste determination might provide new insights into the relationship between foraging genes and division of labor, and accordingly focused on bumblebees, which exhibit size-dependent behavioral caste differentiation. We characterized a foraging gene (Bifor) in bumblebees (Bombus ignitus) and examined the relationship between Bifor expression and size-dependent behavioral caste differentiation. Findings. A putative open reading frame of the Bifor gene was 2004 bp in length. It encoded 668 aa residues and showed high identity to orthologous genes in other hymenopterans (85.3-99.0%). As in ants and wasps, Bifor expression levels were higher in nurses than in foragers. Bifor expression was negatively correlated with individual body size even within the same behavioral castes (regression coefficient = -0.376, P &lt 0.001, all individuals -0.379, P = 0.018, within foragers). Conclusion. These findings indicate that Bifor expression is size dependent and support the idea that Bifor expression levels are related to behavioral caste differentiation in B. ignitus. Thus, the relationship between foraging gene expression and behavioral caste differentiation found in ants and wasps was identified in a different system of labor determination. © 2009 Kawata et al licensee BioMed Central Ltd.

  90. Nitric Oxide Synthase (NOS) in the Japanese Fireflies Luciola lateralis and Luciola cruciata 査読有り

    Hajime Ohtsuki, Jun Yokoyama, Nobuyoshi Ohba, Yoshihiro Ohmiya, Masakado Kawata

    ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 69 (4) 176-188 2008年12月

    出版者・発行元:WILEY-LISS

    DOI: 10.1002/arch.20275  

    ISSN:0739-4462

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    Species-specific flash patterns in firefly species are important for the investigation of the evolution of Lampyridae. Since nitric oxide synthase (NOS) is one of the key enzymes controlling flash patterns, we determined the cDNA sequences of NOS in the Japanese fireflies Luciola lateralis and L. cruciata.. The identity of the NOS sequences was very high between these 2 species. Firefly NOS also exhibited a high identity with those of other insect species, and the cofactor-binding domains were particularly well conserved. Many negatively selected sites were detected throughout the NOS sequences, however, no positive selection was detected. The phylogenetic relationship of insect NOS was different from that of the general classification system, although the lineages corresponded to the major recognized taxonomic groups. Arch. Insect Biochem. Physiol. 69:176-188, 2008. (C) 2008 Wiley-Liss, Inc.

  91. Genetic and acoustic population structuring in the Okinawa least horseshoe bat: are intercolony acoustic differences maintained by vertical maternal transmission? 査読有り

    Hajime Yoshino, Kyle N. Armstrong, Masako Izawa, Jun Yokoyama, Masakado Kawata

    MOLECULAR ECOLOGY 17 (23) 4978-4991 2008年12月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1111/j.1365-294X.2008.03975.x  

    ISSN:0962-1083

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    The origin and meaning of echolocation call frequency variation within rhinolophid bats is not well understood despite an increasing number of allopatric and sympatric examples being documented. A bimodal distribution of mean regional call frequency within the Okinawa-jima Island population of Rhinolophus cornutus pumilus (Rhinolophidae) provided a unique opportunity to investigate geographic call frequency variation early in its development. Individual resting echolocation frequencies, partial mitochondrial DNA D-loop sequences and genotypes from six microsatellite loci were obtained from 288 individuals in 11 colonies across the entire length of the island, and nearby Kume-jima Island. Acoustic differences (5-8 kHz) observed between the north and south regions have been maintained despite evidence of sufficient nuclear gene flow across the middle of the island. Significant subdivision of maternally inherited D-loop haplotypes suggested a limitation of movement of females between regions, but not within the regions, and was evidence of female philopatry. These results support a &apos;maternal transmission&apos; hypothesis whereby the difference in the constant frequency (CF) component between the regions is maintained by mother-offspring transmission of CF, the restricted dispersal of females between regions and small effective population size. We suggest that the mean 5-8 kHz call frequency difference between the regions might develop through random cultural drift.

  92. Message from the editor-in-chief 査読有り

    Masakado Kawata

    Ecological Research 23 (1) 1 2008年1月

    DOI: 10.1007/s11284-007-0446-0  

    ISSN:0912-3814 1440-1703

  93. Role of the 5 '-&gt; 3 ' exonuclease and Klenow fragment of Escherichia coli DNA polymerase I in base mismatch repair 査読有り

    Masaru Imai, Yu-ichiro Tago, Makoto Ihara, Masakado Kawata, Kazuo Yamamoto

    MOLECULAR GENETICS AND GENOMICS 278 (2) 211-220 2007年8月

    出版者・発行元:SPRINGER

    DOI: 10.1007/s00438-007-0239-8  

    ISSN:1617-4615

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    We have previously demonstrated that the Escherichia coli strain mutS Delta polA had a higher rate of transition and minus frameshift mutations than mutS or Delta polA strains. We argued that DNA polymerase I (PolI) corrects transition mismatches. PolI, encoded by the polA gene, possesses Klenow and 5' -&gt; 3' exonuclease domains. In the present study, rates of mutation were found to be higher in Klenow-defective mutS strains and 5' -&gt; 3' exonuclease-defective mutS strains than mutS or polA strains. The Klenow-defective or 5' -&gt; 3' exonuclease-defective mutS strains showed a marked increase in transition mutations. Sites of transition mutations in mutS, Klenow-defective mutS and 5' -&gt; 3' exonuclease-defective mutS strains are different. Thus, it is suggested that, in addition to mutS function, both the Klenow and 5' -&gt; 3' exonuclease domains are involved in the decrease of transition mutations. Transition hot and warm spots in mutS(+) polA(+) strains were found to differ from those in mutS and mutS Delta polA strains. We thus argue that all the spontaneous transition mutations in the wild-type strain do not arise from transition mismatches left unrepaired by the MutS system or MutS PolI system.

  94. A genetically explicit model of speciation by sensory drive within a continuous population in aquatic environments 査読有り

    Masakado Kawata, Ayako Shoji, Shoji Kawamura, Ole Seehausen

    BMC EVOLUTIONARY BIOLOGY 7 99 2007年6月

    出版者・発行元:BIOMED CENTRAL LTD

    DOI: 10.1186/1471-2148-7-99  

    ISSN:1471-2148

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    Background: The sensory drive hypothesis predicts that divergent sensory adaptation in different habitats may lead to premating isolation upon secondary contact of populations. Speciation by sensory drive has traditionally been treated as a special case of speciation as a byproduct of adaptation to divergent environments in geographically isolated populations. However, if habitats are heterogeneous, local adaptation in the sensory systems may cause the emergence of reproductively isolated species from a single unstructured population. In polychromatic fishes, visual sensitivity might become adapted to local ambient light regimes and the sensitivity might influence female preferences for male nuptial color. In this paper, we investigate the possibility of speciation by sensory drive as a byproduct of divergent visual adaptation within a single initially unstructured population. We use models based on explicit genetic mechanisms for color vision and nuptial coloration. Results: We show that in simulations in which the adaptive evolution of visual pigments and color perception are explicitly modeled, sensory drive can promote speciation along a short selection gradient within a continuous habitat and population. We assumed that color perception evolves to adapt to the modal light environment that individuals experience and that females prefer to mate with males whose nuptial color they are most sensitive to. In our simulations color perception depends on the absorption spectra of an individual's visual pigments. Speciation occurred most frequently when the steepness of the environmental light gradient was intermediate and dispersal distance of offspring was relatively small. In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation, whereas we did not observe speciation when peak absorption evolved by stepwise mutations with small effect. Conclusion: The results suggest that speciation can occur where environmental gradients create divergent selection on sensory modalities that are used in mate choice. Evidence for such gradients exists from several animal groups, and from freshwater and marine fishes in particular. The probability of speciation in a continuous population under such conditions may then critically depend on the genetic architecture of perceptual adaptation and female mate choice.

  95. Relative resource abundance explains butterfly biodiversity in island communities 査読有り

    Naoaki Yamamoto, Jun Yokoyama, Masakado Kawata

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 104 (25) 10524-10529 2007年6月

    出版者・発行元:NATL ACAD SCIENCES

    DOI: 10.1073/pnas.0701583104  

    ISSN:0027-8424

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    Ecologists have long been intrigued by the factors that control the pattern of biodiversity, i.e., the distribution and abundance of species. Previous studies have demonstrated that coexisting species partition their resources and/or that the compositional similarity between communities is determined by environmental factors, lending support to the niche-assembly model. However, no attempt has been made to test whether the relative amount of resources that reflects relative niche space controls relative species abundance in communities. Here, we demonstrate that the relative abundance of butterfly species in island communities is significantiy related to the relative biomasses of their host plants but not to the geographic distance between communities. In the studied communities, the biomass of particular host plant species positively affected the abundance of the butterfly species that used them, and consequently, influenced the relative abundance of the butterfly communities. This indicated that the niche space of butterflies (i.e., the amount of resources) strongly influences butterfly biodiversity patterns. We present this field evidence of the niche-apportionment model that propose that the relative amount of niche space explains the pattern of the relative abundance of the species in communities.

  96. Molecular phylogeny and genetic divergence of the introduced populations of japanese guppies, Poecilia reticulata 査読有り

    Ayako Shoji, Jun Yokoyama, Masakado Kawata

    CONSERVATION GENETICS 8 (2) 261-271 2007年4月

    出版者・発行元:SPRINGER

    DOI: 10.1007/s10592-006-9166-1  

    ISSN:1566-0621

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    A phylogenetic tree of guppies from seven introduced Japanese populations was constructed using a mitochondrial gene, and the relationship between these Japanese populations and indigenous South American populations was examined. Phylogenetic trees constructed by maximum parsimony and neighbor joining methods indicated four major groups: Group A: Trinidadian populations; Group B: the northernmost Okinawa populations; Group C: the northern Okinawa populations; Group D: Shimoda populations and the remainder of Trinidadian, Venezuelan, and southern Okinawa populations. Considerable genetic differences were observed among the haplotypes within each Okinawa population similar to that found among haplotypes of different native populations, but not within the Shimoda population, because each Okinawa population included haplotypes belonging to different groups. Genetic differences between Groups B, C, and D might reflect those of the introduced lineages; however, these differences might not result from the divergence after introduction events. These results suggested that multiple introductions of different breeding lineages might cause considerable divergence within and between Okinawa populations.

  97. Effects of temporal and spatial heterogeneities created by consumer-driven nutrient recycling on algal diversity 査読有り

    Satoshi Kato, Jotaro Urabe, Masakado Kawata

    JOURNAL OF THEORETICAL BIOLOGY 245 (2) 364-377 2007年3月

    出版者・発行元:ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.jtbi.2006.10.012  

    ISSN:0022-5193

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    A spatially explicit plant-herbivore model composed of planktonic herbivores, algal preys and nutrients was constructed to examine the effects of consumer-driven nutrient recycling (CNR) on the algal species richness with and without spatial structure. The model assumed that either of two essential nutrients (N and P) limited growth of algal populations and that consumer individuals moved randomly in the lattice and grazed all the algal species with the same efficiency. The results showed that when there was no CNR, the number of persistent algal species was affected by neither supply rates of external nutrients nor spatial structure and was consistently low. When consumers recycled nutrients according to their stoichiometry, the algal species richness changed with supply rates of external nutrients depending on spatial structure: the algal species richness decreased with increasing nutrient loadings when there were no spatial structure because CNR increased the probability of stochastic extinction of algal species by amplifying the oscillation of algae-consumer dynamics. However, when spatial structures were created by the migration of consumers, CNR increased the algal species richness in a range of nutrient loadings because spatial variation of grazing pressure functioned to stabilize the algal-consumer dynamics. The present study suggests that through grazing and nutrient recycling, consumer individuals can create ephemeral heterogeneity in growth environments for algal species and that this ephemerality is one of the keys to understanding algal species in nature. (c) 2006 Elsevier Ltd. All rights reserved.

  98. Impact of ancestral populations on postzygotic isolation in allopatric speciation 査読有り

    TI Hayashi, M Kawata

    POPULATION ECOLOGY 48 (2) 121-130 2006年4月

    出版者・発行元:SPRINGER TOKYO

    DOI: 10.1007/s10144-005-0246-8  

    ISSN:1438-3896

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    Postzygotic isolation evolves due to an accumulation of substitutions (potentially deleterious alleles in hybrids) in populations that have become geographically isolated. These potentially deleterious alleles might also be maintained in ancestral populations before geographic isolation. We used an individual-based model to examine the effect of the genetic state of an ancestral population on the evolution of postzygotic isolation after geographic isolation of a population. The results showed that the number of loci at which degenerative alleles are fixed in an ancestral population at equilibrium significantly affects the evolutionary rates of postzygotic isolation between descendant allopatric populations. Our results suggest that: (1) a severe decrease in population size (e.g., less than ten individuals) is not necessary for the rapid evolution of postzygotic isolation (e.g., &lt; 10,000 generation); (2) rapid speciation can occur when there is a large difference in the equilibrium number of accumulated degenerative alleles between ancestral and descendant populations; and (3) in an ancestral population maintained at a small effective population size for a long period of time, postzygotic isolation rarely evolves if back mutations that restore the function of degenerative alleles are limited.

  99. Genital lock-and-key system and premating isolation by mate preference in carabid beetles (Carabus subgenus Ohomopterus) 査読有り

    T Usami, J Yokoyama, K Kubota, M Kawata

    BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY 87 (1) 145-154 2006年1月

    出版者・発行元:BLACKWELL PUBLISHING

    DOI: 10.1111/j.1095-8312.2006.00562.x  

    ISSN:0024-4066

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    The shapes and lengths of copulatory pieces and vaginal appendices of the carabid beetle subgenus Ohomopterus (genus Carabus) vary among species. In Japan, the species in the group with a medium body size (C. yaconinus, C. iwawakianus, C. maiyasanus, C. uenoi, C. arrowianus, C. esakii, and C. insulicola) are usually allopatric or parapatric, except at Mt Kongosan, where C. uenoi, C. iwawakianus, and C. yaconinus are sympatrically distributed. The degree of premating isolation by mate preference was high between sympatric populations, irrespective of the genetic distance between them. However, premating isolation was absent between parapatric populations. The degree of premating isolation for allopatric populations spanned a wide range of isolation values. Thus, mate discrimination by males seems to have evolved mostly between sympatric pairs. These results suggest two hypotheses. First, premating isolation has evolved through reinforcement or through reproductive character displacement after sympatric contact. Second, premating isolation has evolved in allopatry, and as a result of premating isolation, the species can coexist in sympatry. We also examined the degree of mechanical isolation between C uenoi and C. iwawakianus (a sympatric pair), which have a very large difference in the length of the copulatory piece. The insertion success was low and only one female produced viable offspring among 15 crosses; however, death in females due to copulation was rare. For sympatric matings between C. uenoi and C. iwawakianus, a large difference in the genital size might reduce the gene flow with small mating costs. Gene flow that was significantly reduced by genital difference might cause either the evolution of premating isolation through reinforcement/reproductive character displacement or through the maintenance of a high degree of premating isolation following sympatric contact. (c) 2006 The Linnean Society of London.

  100. Geographic differences in flash intervals and pre-mating isolation between populations of the Genji firefly, Luciola cruciata 査読有り

    M Tamura, J Yokoyama, N Ohba, M Kawata

    ECOLOGICAL ENTOMOLOGY 30 (2) 241-245 2005年4月

    出版者・発行元:BLACKWELL PUBLISHING LTD

    DOI: 10.1111/j.0307-6946.2005.00683.x  

    ISSN:0307-6946

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    1. Two types of Genji firefly, Luciola cruciata, have been recognised on the basis of the inter-flash interval. 2. The fast-flash and slow-flash type fireflies, distributed in the western and eastern parts of Japan, exhibit a 2- and 4-s interval of bioluminescence flash, respectively. In addition, an intermediate-flash type is found on the boundary between these two regions. 3. The differences in the responses of the males of four field populations to different intervals of artificial flashes were examined. 4. The results revealed that in the Aomori and Sendai populations (slow-flash type), a significantly larger number of males approached the 4- and 5-s flash intervals than approached the 2- and 3-s intervals of artificial flashes. On the other hand, in the Ohtsu population (fast-flash type), a significantly larger number of males approached the 2- and 3-s flash intervals than the 4- and 5-s intervals of artificial flashes. The Inuyama population (intermediate-flash type) did not show any particular preferences to flash intervals. 5. This study shows that in firefly populations, geographic variation in flash pattern can cause some degree of pre-mating isolation between populations.

  101. Absence of strand bias for deletion mutagenesis during chromosomal leading and lagging strand replication in Escherichia coli 査読有り

    Yuki Nagata, Genta Kawaguchi, Yu-Ichiro Tago, Masaru Imai, Takashi Watanabe, Shigehisa Sakurai, Makoto Ihara, Masakado Kawata, Kazuo Yamamoto

    Genes and Genetic Systems 80 (1) 1-8 2005年2月

    DOI: 10.1266/ggs.80.1  

    ISSN:1341-7568

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    Investigations were carried out to determine whether both DNA strands involved in Escherichia coli chromosomal DNA replication are replicated with similar accuracy. Experiments consisted of measuring the forward mutation rate from tonB+ to tonB- in pairs of polA deficient strains in which the chromosomal target gene tonB was oriented in the two possible directions relative to the origin of replication, oriC. Within these pairs, the tonB sequence would be subjected to leading strand replication in one orientation and to lagging strand replication in the other. The most common tonB mutations in the polA1 strain were deletions followed by frameshifts. Among the deletions, a strong hotspot site with a 13-base deletion in the polA1 strains accounted for 18 of the 33 deletions in the one orientation, and 31 of the 58 deletions in the other. The results suggested that the two strands were replicated with equal or similar accuracy for deletion formation.

  102. The choice of oviposition site and the effects of density and oviposition timing on survivorship in Rana japonica 査読有り

    N Matsushima, M Kawata

    ECOLOGICAL RESEARCH 20 (1) 81-86 2005年1月

    出版者・発行元:SPRINGER TOKYO

    DOI: 10.1007/s11284-004-0010-0  

    ISSN:0912-3814

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    In species that lack parental care and whose larvae are restricted to a given space throughout development, choice of egg-laying or reproductive sites often greatly influences fitness. Furthermore, reproductive success of individuals may be affected not only by conditions of the breeding area but also by the time when they start to breed, because intraspecific variation in the timing of breeding may result in asymmetric competition between larvae. We addressed these issues in an experimental and field study of the Japanese brown frog, Rana japonica. We tested whether the survival success of larvae decreased with an increase in the number of deposited egg masses and with a greater delay in oviposition. We found that the number of egg masses and timing of oviposition together significantly predicted larval survival per clutch. Moreover, we observed the natural oviposition of R. japonica to examine the prediction that if the density of larvae and the timing of oviposition affect survivorship of larvae, R. japonica will avoid depositing eggs in pools in which egg masses have already been deposited. We found that for small pools only, R. japonica tended to favor oviposition at unoccupied pools (those lacking egg masses and larvae) in the spawning season. For large pools, however, adults favored those already occupied by egg masses in the spawning period. The density of egg masses and tadpoles or the timing of oviposition may have less effect on spawning or the survival of tadpoles in large pools than in small pools.

  103. The effects of spatial habitat structure on the evolution of density-dependent growth and reproduction in freshwater snails 査読有り

    Masakado Kawata, Hiroshi Sawada, Jun Yokoyama, Lázaro M. Echenique-Díaz, Yasuyuki Ishibashi

    Hydrobiologia 533 (1) 229-241 2005年1月

    DOI: 10.1007/s10750-004-2740-y  

    ISSN:0018-8158

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    We examined the growth and reproductive rates of freshwater snails, Physa acuta, in two habitat types. In the Asabata habitat, snails lived in isolated water pools, which occasionally joined to form a single large pool in the Kakegawa habitat, they lived in a slow-running water way. Genetic structure assessments using three microsatellite loci supports the idea that a stable panmictic population occupies the Kakegawa habitat. The Asabata habitat, however, is occupied with an alternate mixing population as revealed by microsatellite data. The Asabata population might alternate between localized mating within isolated pools (as revealed by high F IS and F IT values) when the water levels are low and panmixia (as revealed by the low F ST values and AMOVA analysis) when the habitat is flooded. Laboratory experiments, using snails collected from the two habitats, showed that juvenile snails grew faster, laid more eggs, and laid them earlier in the Asabata habitat than in the Kakegawa habitat. Growth rates were lower at high density than at low density in the Kakegawa habitat the inverse was true in the Asabata habitat. Density-dependent response of individual snail reproduction was higher in the Kakagawa habitat than in the Asabata habitats. The results support the hypothesis that spatial structure affects the evolution of density-dependent growth rates and of timing for reproduction. © Springer 2005.

  104. Role of the RuvAB protein in avoiding spontaneous formation of deletion mutations in the Escherichia coli K-12 endogenous tonB gene 査読有り

    K Mashimo, Y Nagata, M Kawata, H Iwasaki, K Yamamoto

    BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 323 (1) 197-203 2004年10月

    出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE

    DOI: 10.1016/j.bbrc.2004.08.078  

    ISSN:0006-291X

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    The endogenous tonB gene of Escherichia coli was used as a target for spontaneous deletion mutations which were isolated from ruvAB(-), recG(-), and ruvC(-) cells. The rates of tonB mutation were essentially the same in;ruv(+), ruvAB(-), recG(-), and ruvC(-) cells. We analyzed tonB mutants by sequencing. In the ruv(+), recG(-), and ruvC(-) strains, the spectra were different from those obtained from the ruvAB- cells, where deletions dominated followed by IS insertions, base substitutions, and frameshifts, in that order. We then analyzed the tonB-trp large deletion, due to simultaneous mutations of the trp operon, and found that the frequency in ruvAB(-) was higher than those in ruv(+), recG(-), and ruvC(-) cells. To characterize deletion formation further, we analyzed all the tonB mutants from one colicin plate. Seven deletions were identified at five sites from the 45 tonB mutants of ruv(+) cells and 24 deletions at 11 sites from the 43 tonB mutants of ruvAB(-) cells. Thus, the ruvAB(-) strain is a deletion mutator. We discuss the role of RuvAB in avoiding deletions. (C) 2004 Elsevier Inc. All rights reserved.

  105. Characterization of 17 microsatellite loci in the Japanese land snail genera Mandarina, Ainohelix, and Euhadra (Mollusca, Gastropoda, Pulmonata) 査読有り

    A Davison, S Chiba, M Kawata

    MOLECULAR ECOLOGY NOTES 4 (3) 423-425 2004年9月

    出版者・発行元:BLACKWELL PUBLISHING LTD

    DOI: 10.1111/j.1471-8286.2004.00680.x  

    ISSN:1471-8278

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    Land snails of the genera Mandarina, Euhadra and Ainohelix are useful for understanding the ecology and evolution of speciation and adaptation, so we have developed 17 microsatellite loci for these species. As in other land snails, most of the loci are highly polymorphic compound repeats, with a great size range between alleles. The loci should be useful in understanding gene-flow, genetic structure and speciation in these species.

  106. A new hypothesis for species coexistence: male-male repulsion promotes coexistence of competing species 査読有り

    OK Mikami, M Kohda, M Kawata

    POPULATION ECOLOGY 46 (2) 213-217 2004年8月

    出版者・発行元:SPRINGER TOKYO

    DOI: 10.1007/s10144-004-0189-5  

    ISSN:1438-3896

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    We propose a new hypothesis for species coexistence by considering behavioral interactions between individuals. The hypothesis states that repulsive behavior between conspecific males (male-male repulsion) creates space for competing species, which promotes their coexistence. This hypothesis can explain the coexistence of two competing species even when their ecological niches completely overlap in spatially homogeneous environments. In addition, the mechanisms underlying such behavior might play a role in enabling the coexistence of two species immediately after speciation, with little or no niche differentiation, as in the case of cichlid fish communities, for example. Although there is limited evidence supporting this hypothesis, it can nevertheless explain the occurrence of species coexistence and biodiversity, which cannot be explained by previous theories.

  107. Does interspecific territoriality reflect the intensity of ecological interactions? - A theoretical model for interspecific territoriality 査読有り

    OK Mikami, M Kawata

    EVOLUTIONARY ECOLOGY RESEARCH 6 (5) 765-775 2004年7月

    出版者・発行元:EVOLUTIONARY ECOLOGY LTD

    ISSN:1522-0613

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    In many studies, interspecific territorial behaviours among co-existing species have been used to infer the presence and the intensity of underlying ecological interactions between species, mainly resource competition. However, the theoretical background of this inference is insufficient. Hence. we constructed a simple theoretical model of interspecific territoriality assuming that interspecific territorial defence is the optimal behaviour. We discuss the factors promoting interspecific territoriality and the relationship between interspecific territoriality and ecological interactions. The model predicts that: (1) a territory holder preferentially excludes intruders of species with high 'exclusion efficiency's (2) the decision by the territory holder to exclude a certain species or not does not depend on the probability of finding intruders of the species or on the number of intrusions by the species, and (3) interspecific territoriality does not always reflect the intensity of ecological interactions between species. These results indicate that the observation of interspecific territoriality does not necessarily indicate the intensity of ecological interactions. In addition, if territory holders defend their territories as predicted by the present optimal model, the co-existence of competing species is promoted.

  108. Evolution of rumours that discriminate lying defectors 査読有り

    M Nakamaru, M Kawata

    EVOLUTIONARY ECOLOGY RESEARCH 6 (2) 261-283 2004年2月

    出版者・発行元:EVOLUTIONARY ECOLOGY LTD

    ISSN:1522-0613

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    Discrimination of defectors is the key to the evolution of cooperation. In this paper, we examine the effect of rumours on the evolution of cooperation. 'Rumour' is defined as spreading or starting a reputation (concerned with cooperativeness of players), which is passed from one player to another. If players receive a rumour that a given player is a defector, they can avoid being defected by that player. However, to establish and maintain their cooperative relationship, players must also be able to distinguish incorrect rumours from correct ones because the rumour might be untrue. The speed of spreading an incorrect rumour is expected to affect its likelihood of detection and the consequences of detection. In computer simulations (individual-based simulation model), a pair (chosen randomly) plays the Prisoner's Dilemma game once. Each strategy consists of three rules: (1) a rule for the Prisoner's Dilemma game; (2) a rule for spreading a rumour; and (3) a rule for starting rumours. We consider 39 strategies in total. Then we classify strategies into several groups. The ADVISOR group of strategies, whose members are cooperative and start rumours about defectors, is not invaded by the LIAR group, whose members are defectors who tell lies, saying 'I'm cooperative'. ADVISOR (as a group) is not invaded by LIAR even though given pairs (one from each group) seldom meet more than once. If a correct rumour is seldom received, however, and if an incorrect rumour spreads quickly, members of ADVISOR (i.e. members that use strategies from the ADVISOR group) are confused by the incorrect rumour. As a result, ADVISOR is invaded by LIAR. As another group of strategies, we consider CONDITIONAL_ADVISOR, of which each representative member only spreads rumours received from other players who have cooperated with him. Unlike ADVISOR, CONDITIONAL_ADVISOR is able to refuse being invaded by LIAR. On the other hand, if the same conditions hold, but the cooperative strategy is instead based on the individual's own past experience, that group is invaded by LIAR. This implies that a rumour evolves if cooperators can, using that rumour, detect and punish cheaters - especially a lying defector.

  109. The evolution of extreme shell shape variation in the land snail Ainohelix editha: a phylogeny and hybrid zone analysis 査読有り

    H Teshima, A Davison, Y Kuwahara, J Yokoyama, S Chiba, T Fukuda, H Ogimura, M Kawata

    MOLECULAR ECOLOGY 12 (7) 1869-1878 2003年7月

    出版者・発行元:BLACKWELL PUBLISHING LTD

    DOI: 10.1046/j.1365-294X.2003.01862.x  

    ISSN:0962-1083

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    Ainohelix editha from Hokkaido, Japan, exhibit great geographical variation in their shell morphology. In particular, A. editha in two quite separate locations, Shimamaki and Samani, are striking because they are extremely flat and have a sharp keel, whereas at adjacent sites the shells are globular or depressed-globular. We used mitochondrial 16S rRNA and nuclear ITS-2 sequences to infer a phylogeny among 47 snails from 29 locations. Snails from the two keeled-flat populations clustered separately in the phylogeny, suggesting that this unusual shell form could have evolved independently. A morphological analysis of shells collected along a transect between keeled-flat and globular snail sites showed a cline for shell shape and the angle of the keel. Two different mtDNA lineages were found across the transect, with a cline for an ITS-2 single nucleotide polymorphism. Together, the results may suggest a lack of reproductive isolation between keeled-flat and globular snails, with possible introgression by hybridization.

  110. Roles of the RecJ and RecQ proteins in spontaneous formation of deletion mutations in the Escherichia coli K12 endogenous tonB gene 査読有り

    K Mashimo, M Kawata, K Yamamoto

    MUTAGENESIS 18 (4) 355-363 2003年7月

    出版者・発行元:OXFORD UNIV PRESS

    DOI: 10.1093/mutage/geg004  

    ISSN:0267-8357

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    The endogenous tonB gene of Escherichia coli was used as a target for spontaneous deletion mutations which were isolated from recJ(-) and recQ(-) cells. Large deletions, due to simultaneous mutations of the trp operon, were also isolated. The rates of tonB mutation were 2.77 x 10(-8), 4.13 x 10(-8) and 5.00 x 10(-8) for rec(+), recJ(-) and recQ(-) cells, respectively. We analyzed 94 and 99 tonB mutants from the recJ(-) and recQ(-) cells, respectively, by sequencing. We found that IS insertion dominated, followed by base substitutions, frameshifts and deletions in both recJ(-) and recQ(-) strains. We then analyzed 55 tonB-trp deletions, ranging in size from 5907 to 20 832 bp, from the recJ(-) strains and 47 tonB-trp deletions, ranging in size from 4959 to 16 390 bp from the recQ(-) strains. About one-third of tonB-trp deletions from both the recJ(-) and the recQ(-) cells were found to have occurred between short sequence repeats at the deletion termini. About one-third of tonB-trp deletions from both mutants showed 2-4 bp repeats in the immediate vicinity of the endpoints, which appeared to indicate no clear association with deletion. The remaining one-third of tonB-trp deletions had no homology at the endpoint. These results were similar to those for the rec(+) cells. Hanada and colleagues demonstrated that structually similar rearrangements arising during lambda bio phage formation (illegitimate recombination) increased in the recQ(-) strain. To explain this discrepancy, we interpreted as distinctive the mechanism for rearrangement during transducing phage formation which is recQ-dependent and that for deletions formed in chromosomes which is recQ-independent.

  111. X-ray-induced mutations in Escherichia coli K-12 strains with altered DNA polymerase I activities 査読有り

    Y Nagata, M Kawata, J Komura, T Ono, K Yamamoto

    MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS 528 (1-2) 93-103 2003年7月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0027-5107(03)00100-3  

    ISSN:0027-5107

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    Spectra of ionizing radiation mutagenesis were determined by sequencing X-ray-induced endogenous tonB gene mutations in Escherichia coli polA strains. We used two polA alleles, the polA1 mutation, defective for Klenow domain, and the polA107 mutation, defective for flap domain. We demonstrated that irradiation of 75 and 50 Gy X-rays could induce 3.8- and 2.6-fold more of tonB mutation in polA1 and polA107 strains, respectively, than spontaneous level. The radiation induced spectrum of 51 tonB mutations in polA1 and 51 in polA107 indicated that minus frameshift, A:T --&gt; T:A transversion and G:C --&gt; T:A transversion were the types of mutations increased. Previously, we have reported essentially the same X-ray-induced tonB mutation spectra in the wild-type strain. These results indicate that (1) X-rays can induce minus frameshift, A:T --&gt; T:A transversion and G:C ---&gt; T:A transversion in E. coli and (2) presence or absence of polymerase I (PolI) of E. coli does not have any effects on the process of X-ray mutagenesis. (C) 2003 Elsevier Science B.V All rights reserved.

  112. Evolution of biodiversity through divergent processes: Theories and facts II. Empirical studies 査読有り

    Masakado Kawata

    Population Ecology 44 (3) 127-128 2002年12月

    DOI: 10.1007/s101440200015  

    ISSN:1438-3896

  113. How genes causing unfit hybrids evolve within populations: a review of models of postzygotic isolation 査読有り

    TI Hayashi, M Kawata

    POPULATION ECOLOGY 44 (3) 157-163 2002年12月

    出版者・発行元:SPRINGER-VERLAG TOKYO

    DOI: 10.1007/s101440200019  

    ISSN:1438-3896

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    The main subject for models of postzygotic isolation has been how reproductive isolation genes (RI genes) which cause hybrid inviability or sterility spread within populations despite their deleterious effects. The models are divided into three categories according to the within-population effect of RI genes in their fixation process. (1) The beneficial effect model, where RI genes are assumed to spread within populations by a positive selective force via natural or sexual selection. (2) The neutral effect model, where RI genes are assumed not to affect the fitness of individuals in their fixation process and to be spread by genetic drift. (3) The deleterious effect model, where RI genes are assumed to exhibit some (slightly) deleterious effects in their fixation process and to be spread by genetic drift. Factors that affect the applicability of these models are discussed. If a selective force such as sexual conflict or natural selection facilitates the evolution of RI genes, the beneficial effect model should be applied. Many empirical studies have suggested that positive selection plays an important role in the evolution of hybrid male sterility. If the mutation rates of 91 genes are low, and the specificity of epistatic interaction causing hybrid inviability or sterility is high, the neutral effect model,should be applied. However, if the opposite condition applies, the deleterious effect model should be applied.

  114. Characterization of spontaneous mutation in the ΔsoxR and SoxS overproducing strains of Escherichia coli 査読有り

    Eiji Yamamura, Eun Hye Lee, Akihiro Kuzumaki, Norio Uematsu, Tatsuo Nunoshiba, Masakado Kawata, Kazuo Yamamoto

    Journal of Radiation Research 43 (2) 195-203 2002年6月

    DOI: 10.1269/jrr.43.195  

    ISSN:0449-3060

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    To examine the role of the soxRS regulon in mutagenesis, we characterized the spontaneous mutations occurring in the endogenous tonB gene in the ΔsoxR strain and the SoxS overproducing strain of Escherichia coli. Neither the ΔsoxR strain nor the SoxS overproducing strain led to an enhancement or diminishment of the spontaneous mutation frequency. By DNA sequencing, we determined 50 spontaneous mutants from the ΔsoxR strains, and found that 36% were both base substitutions and IS insertions, 14% frameshifts and 10% deletions. Among the base substitutions, G:C→T:A transversions and G:C→A:T transitions predominated, followed by A:T→T:A transversions. We determined 54 spontaneous mutants from the SoxS overproducing strains, and found that 37% were IS insertions, 31% base substitutions, 17% frameshifts, 9% deletions and 6% duplications. Among the base substitutions, G:C→T:A transversions dominated, followed by A:T→T:A transversions and G:C→A:T transitions. These results were similar to those from the soxRS+ strains. Thus, it is suggested that the soxRS-regulated genes do not play a significant role in the defense against spontaneous mutagenesis.

  115. How genes causing unfit hybrid evolve within population?: A review for models of postzygotic isolation 査読有り

    Hayashi I.T, Kawata M

    Population Ecology 43 179-188 2002年

  116. Isolation and characterization of microsatellite loci in the Bangユs leaf-nosed bat Hipposideros turpis 査読有り

    Echenique L. M, J. Yokoyama, M. Kawata, S. Abe, Y. Ishibashi

    Molecular Ecology Notes 2: 398-401 2 398-401 2002年

    DOI: 10.1046/j.1471-8286.2002.00250.x  

  117. The roles of Klenow processing and flap processing activities of DNA polymerase I in chromosome instability in Escherichia coli K12 strains 査読有り

    Y Nagata, K Mashimo, M Kawata, K Yamamoto

    GENETICS 160 (1) 13-23 2002年1月

    出版者・発行元:GENETICS

    ISSN:0016-6731

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    The sequences of spontaneous mutations occurring in the endogenous tonB gene of Escherichia coli in the DeltapolA and polA107 mutant strains were compared. Five categories of mutations were found: (1) deletions, (2) minus frameshifts, (3) plus frameshifts, (4) duplications, and (5) other mutations. The DeltapolA strain, which is deficient in both Klenow domain and 5' --&gt; 3' exonuclease domain of DNA polymerase 1, shows a marked increase in categories 1-4. The polA107 strain, which is deficient in the 5' --&gt; 3' exonuclease domain but proficient in the Klenow domain, shows marked increases in categories 3 and 4 but not in 1 or 2. Previously, we reported that the polA1 strain, which is known to be deficient in the Klenow domain but proficient in the 5' --&gt; 3' exonuclease domain, shows increases in-categories 1 and 2 but not in 3 or 4. The 5' --&gt; 3' exonuclease domain of DNA polymerase I is a homolog of the mammalian FEN1 and the yeast RAD27 flap nucleases. We therefore proposed the model that the Klenow domain can process deletion and minus frameshift mismatch in the nascent DNA and that flap nuclease can process plus frameshift and duplication mismatch in the nascent DNA.

  118. The effects of individual interactions and habitat preferences on spatial structure in a grassland bird community 査読有り

    Osamu K. Mikami, Masakado Kawata

    Ecography 25 (2) 200-214 2002年

    DOI: 10.1034/j.1600-0587.2002.250208.x  

    ISSN:0906-7590

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    Spatial structure and the distribution of individuals within a community might be influenced by several factors such as habitat heterogeneity and local interactions among individuals of the same and different species. We investigated the spatial distributions of eight bird species in a grassland community during the breeding season and examined whether the spatial distributions of individuals were influenced by interactions among neighboring individuals or different habitat preferences of different bird species. In order to identify the effects of the interactions among neighboring individuals and habitat preference, we developed a randomization test in which species identifications were randomly allocated to the observed individual positions within areas with the same vegetation structure. The randomization test indicated that individuals tend to have territories near the territories of individuals of the same species or of a particular species more frequently (or less frequently) than those expected from random distributions of individuals. Among these associations, only one case was explained by individual interactions, and 19 cases were explained by habitat preference. The results suggest that both individual interactions and habitat preference affected the spatial distributions of individuals and possibly influence the species compositions and diversity in grassland bird communities.

  119. Invasion of vacant niches and subsequent sympatric speciation 査読有り

    M Kawata

    PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES 269 (1486) 55-63 2002年1月

    出版者・発行元:ROYAL SOC

    DOI: 10.1098/rspb.2001.1846  

    ISSN:0962-8452

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    An individual-based simulation study was conducted to examine the population dynamics of 'invasion of a vacant niche' and subsequent speciation (by reproductive isolation) when food resources are randomly distributed spatially within the habitat and the frequencies of different food types are bimodally distributed (i.e. smaller and larger sizes of food being most abundant). The initially vacant niche was that of unused larger sizes of food. When phenotypic variation for resource use (i.e. food sizes) was small in the initial population, and each female could choose a mate from anywhere in the habitat, the population could not invade the vacant niche. But when the dispersal distance of the offspring and the area within which a female could choose a mate were small (i.e. the genetic neighbourhood size was small), the population could, in most cases, evolve to use both smaller and larger food sizes and form sister species sympatrically, with each species utilizing one of the two niches (small and large sizes of food). When phenotypic variation in resource use in the initial population was large, the population could, in most cases, invade the vacant niche by evolving to use both smaller and larger sizes of food. The probability of speciation increased as the dispersal distance of offspring decreased. The results indicate that populations whose individuals have small Wright's genetic neighbourhoods may often exploit a vacant niche and diversify sympatrically in the process.

  120. The influence of neighborhood size and habitat shape on the accumulation of deleterious mutations 査読有り

    M Kawata

    JOURNAL OF THEORETICAL BIOLOGY 211 (3) 187-199 2001年8月

    出版者・発行元:ACADEMIC PRESS LTD

    DOI: 10.1006/jtbi.2001.2268  

    ISSN:0022-5193

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    To examine the impact of genetic neighborhood size and habitat shape on genetic load and the accumulation of deleterious mutation, individual-based simulations were performed in continuously distributed habitats. The risk of extinction increased as both the area of the habitat and the neighborhood size decreased. When the neighborhood area became smaller than the habitat area, habitat shape also began to influence the risk of extinction by mutation loads, expected time to extinction being shorter in longer and narrower habitats than in a square habitat. Both the number of homozygous deleterious loci per individual and the mutation load in the population increased as the neighborhood size and total population size decreased. Neighborhood size and total population size both independently affected the average number of homozygous deleterious loci per individual. In addition, as the ratio of the long to the short side of the rectangle of a habitat increased, the average number of homozygous deleterious loci increased. When the areas of the habitats were held constant, the average number of homozygous loci and the mutation loads were smallest for a regular square and largest for the longest, narrowest habitat. These results suggest that the spatial genetic structure of an individual is an important factor in the accumulation of deleterious mutations and the risk of extinction by mutation meltdown. (C) 2001 Academic Press.

  121. The dybamics of the spatial micro-distribution of periphyton and the influence of grazing by snails. 査読有り

    Kawata M, Hayashi M, Hara T

    Oikos 92 404-416 2001年4月

  122. Interaction between neighboring algae and snail grazing in structuring microdistribution patterns of periphyton 査読有り

    KAWATA Masakado

    Oikos 92 404-406 2001年

  123. An in Vivo approach to identifying sequence context of 8-oxoguanine mutagenesis 査読有り

    Takashi Watanabe, Tatsuo Nunoshiba, Masakado Kawata, Kazuo Yamamoto

    Biochemical and Biophysical Research Communications 284 (1) 179-184 2001年

    出版者・発行元:Academic Press Inc.

    DOI: 10.1006/bbrc.2001.4946  

    ISSN:0006-291X

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    Base substitution mutations are not distributed randomly in that most are located at a few specific hotspots sites. We have been studying 7,8-dihydro-8-oxoguanine mutagenesis in Escherichia coli in the supF gene carried in a plasmid. Among hotspots, guanine within the 5′-AGA-3′ located in the anticodon site was susceptible to the induction of G:CT→:A transversion. In this study, we constructed variants of the supF gene in which the hotspot 5′-AGA-3′ was modified to 5′-AGT-3′, 5′-AGG-3′ and 5′-AGC-3′ to determine the influence of 3′ neighboring base on G:C→T:A mutational activity. Using these variant supF genes propagated in a 7,8-dihydro-8-oxoguanine repair-deficient host, we found that guanine within 5′-AGA-3′ and 5′-AGG-3′ produce G:C→T:A, but guanine within 5′-AGT-3′ and 5′-AGC-3′ reduce the formation of G:C→T:A. These changes were thus due to the effect of sequence context on the efficiency of mutation formation at the sites of 7,8-dihydro-8-oxoguanine. We also observed a longer range base-pair effect on hotspot formation. © 2001 Academic Press.

  124. Evolution of postmating isolation: Comparison of three models based on possible genetic mechanisms 査読有り

    T. I. Hayashi, M. Kawata

    Population Ecology 43 (2) 179-188 2001年

    出版者・発行元:Springer Japan

    DOI: 10.1007/PL00012028  

    ISSN:1438-3896

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    In this study, we simulated the process of the evolution of postmating isolation using three models in which postmating isolation is caused by (1) genetic divergence through collaborative coevolution, (2) genetic divergence through antagonistic coevolution resulting from sexual conflict, and (3) genetic divergence through combinational incompatibility. The collaborative coevolution model and the combinational incompatibility model showed a similar decreasing pattern of hybrid compatibility over generations depending on population size and mutation rates. The antagonistic coevolution model showed that reproductive isolation can evolve rapidly depending on the intensity of selection. In the combinational incompatibility model, the increasing number of loci that interact and result in incompatibility would have both promoting and inhibiting effects on the formation of hybrid incompatibility in the earlier stage of isolation. Mutation rates for genes causing incompatibility significantly affect the number of generations required for postmating isolation, which indicates that models assuming high mutation rates (e.g., μ = 10-4) might predict much faster evolution for reproductive isolation than those observed in real populations.

  125. Speciation by sexual selection in hybridizing populations without viability selection 査読有り

    M Kawata, J Yoshimura

    EVOLUTIONARY ECOLOGY RESEARCH 2 (7) 897-909 2000年11月

    出版者・発行元:EVOLUTIONARY ECOLOGY LTD

    ISSN:1522-0613

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    We propose a new speciation mechanism for hybridizing populations based on frequency-dependent sexual selection theory. In contrast to previous reinforcement and symmetric speciation models, this model does not require viability selection for male sexual traits, selection against unlit hybrids or disruptive selection for ecological traits. The model assumes that females exhibit mating preferences based on male secondary sexual characters. Both female mating preferences and male secondary sexual traits are independent quantitative genetic traits. Females choose using one of five tactics All individuals, including the hybrids, have the same ability to survive and reproduce. Two populations that differ only in their average values of female preference and male sexual traits are assumed to come into contact and hybridize. Most cases of the model frequently result in complete prezygotic isolation. The likelihood of speciation decreases with the degree of phenotypic overlap between the two merging populations. However, the probability of speciation is not zero even when the two merging populations are identical.

  126. The effect of spatial habitat structure on population variability of freshwater snails 査読有り

    KAWATA Masakado

    Hydrobiologia 429 157-167 2000年

  127. Characterization of spontaneous mutation in the oxyR strain of Escherichia coli. 査読有り

    Yamamura,E.」「T, Nunoshiba」「M. Kawata」「K. Yamamoto」

    Biochemical and Biophysical Research Communications 279 427-422 2000年

    DOI: 10.1006/bbrc.2000.3961  

  128. The effects of dispersal behaviour in group selection 査読有り

    M Kawata

    EVOLUTIONARY ECOLOGY RESEARCH 1 (6) 663-680 1999年10月

    出版者・発行元:EVOLUTIONARY ECOLOGY LTD

    ISSN:1522-0613

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    Individual-based simulations were conducted to examine the spread of an altruistic allele by group selection. For the simulations, individuals with one locus determining altruistic behaviour were created in an environment with 13 patches. Individual fitness was determined by the number of altruists and the number of total individuals in a patch. Offspring disperse within the natal patch or into neighbouring patches depending on random values with a normal distribution having a zero mean and standard deviation sigma(d) (random dispersal model). The probability of the spread of the altruistic allele increased with increasing dispersal distance until a moderately low dispersal distance (sigma(d) = 50); thereafter, the probability decreased with increasing dispersal distance. A density-dependent dispersal model in which female offspring tend to disperse to the patch with lowest densities among five candidate dispersal sites was also tested. For the density-dependent dispersal model, the chance of spreading the altruistic allele was higher than that of the random dispersal model. The results can be explained by two components of group selection: the extinction of groups with lower frequencies of altruists (selective extinction) and higher frequencies of migrants of altruists due to high productivities of altruistic groups (effective migrants). Evolution of altruism by interdemic group selection only (i.e. by differential extinctions and recolonization of demes) appears unlikely, since it requires high rates of both extinction and recolonization with low migration among surviving demes. However, the present study showed that moderately low migration can create favourable conditions under which both selective extinction and effective migrants simultaneously increase the probability of spreading the altruistic alleles.

  129. Perceptual scales of spatial heterogeneity of periphyton for freshwater snails 査読有り

    M Kawata, H Agawa

    ECOLOGY LETTERS 2 (4) 210-214 1999年7月

    出版者・発行元:WILEY-BLACKWELL

    DOI: 10.1046/j.1461-0248.1999.00071.x  

    ISSN:1461-023X

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    The hypothesis that individuals recognize their environment as homogeneous when the scales of spatial heterogeneity of resources are smaller than a certain scale, but can distinguish them as patches when they are larger than that scale was tested using freshwater snails (Physa acuta) in various distributions in periphyton environments. In a pattern of periphyton distribution in which the size of algal cells was 47 mm, individuals moved significantly more slowly on algal cells than on nonalgal cells. However, in other patterns in which the sizes of algal cells were 23.5 mm and 15.7 mm, the speeds of individuals on algal and nonalgal cells were not significantly different. These results support the hypothesis that individuals use the environment homogeneously when the scales of spatial heterogeneity of resources are smaller than a certain scale, but they can distinguish between patches when the scales are larger.

  130. Social organization of the vole Clethrionomysonzys rufocanus and its demographic and genetic consequences: a review 査読有り

    Y Ishibashi, T Saitoh, M Kawata

    RESEARCHES ON POPULATION ECOLOGY 40 (1) 39-50 1998年6月

    出版者・発行元:SPRINGER TOKYO

    DOI: 10.1007/BF02765220  

    ISSN:0034-5466

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    Recent findings on the relationship between social interaction and demographic process in the gray-sided vole Clethrionomys rufocanus are reviewed with reference to the findings in other microtine rodents. Social behavior was particularly focused on spacing and dispersal, and their effects on population dynamics are discussed. Female territoriality can limit a population abundance as a density-dependent factor, although its regulatory effect is controversial. Female philopatry and male-biased dispersal should bring about the clumped distribution of female relatives and genetically random distribution of males during the breeding season. The sexual difference in dispersal patterns can contribute to the mating behavior of the vole; promiscuous mating and low frequency of incestuous mating. However, effects of social structure, including kinship, on reproduction and survival of individuals still remains to be clarified. Molecular markers may help to solve these issues and provide new field of population ecology in microtine rodents.

  131. The role of male dispersal in evolution of altruistic behavio 査読有り

    Kawata, M

    Shoji, A., J. Yokoyama and M. Kawata. (in press) Molecular phylogeny and genetic divergence of the introduced populations of Japanese guppies, Poecilia reticulata. Conservation Genetics. 13 367-375 1998年

    DOI: 10.1046/j.1440-1703.1998.00276.x  

  132. Exploitative competition and ecological effective abundance 査読有り

    M Kawata

    ECOLOGICAL MODELLING 94 (2-3) 125-137 1997年1月

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/S0304-3800(96)00008-7  

    ISSN:0304-3800

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    This study analyzes the effect of exploitative competition and density dependence by using an individual-based simulation model. There are two components of exploitative competition (leftovers and resource-recovery competition). In leftovers competition, individuals compete for food resources that have been left by others. In resource-recovery competition, the consumption of foods by individual predators affects growth rates of food populations. An individual-based simulation was conducted to examine how these two types of competition affect density-dependent processes. In the simulation, individual predators search for food organisms within their home range. Food organisms reproduce in three different ways: replacement, recruitment and neighborhood recruitment. In replacement all food organisms die and are replaced with a new food population. In recruitment, food organisms do not disappear during simulation unless they are eaten by predators, and new food organisms are recruited based on their density, In neighborhood recruitment, food organisms reproduce depending on their abundance within the neighborhood area. The simulation was conducted by varying the number of predators, the home range size of individual predators, the area of simulation, the reproductive rates of food organisms, and the reproductive modes of the food organisms. The number of food organisms taken by an individual predator, and the number of predators over several different scales, were measured. A multiple regression was conducted to examine the relationships between several different estimations of predator abundance and the number of food organisms taken by an predator. The effects of different types of exploitative competition differed depending upon the spatial scale or estimated population density. The number of predators within the home range of an individual predator is negatively related to individual food gain. This suggests that leftovers competition can be detected within the home range of an individual predator. In the case in which the food population was regulated over the whole simulation area, the number of predators in the whole area was positively related to food gain of individual predator in the case of recruitment and neighborhood recruitment of reproduction of food, but positively in replacement. In the case in which a food population was regulated in smaller parts of the whole area, the estimated number of predators within a food population were related to food gain of an individual predator but the total population size does not affect the food gain. (C) 1997 Elsevier Science B.V.

  133. Morphological stasis and phylogenetic relationships in Tadpole shrimps(Triops) 査読有り

    KAWATA Masakado

    Biological Journal of Linnean Society 61 439-457 1997年

    DOI: 10.1006/bijl.1997.0138  

  134. The effect of neighborhood densities or reproductive success 査読有り

    KAWATA Masakado

    Ecoscience 4 465-469 1997年

  135. The loss of genetic variability in a fragmented continuous population 査読有り

    KAWATA Masakado

    Researches on Population Ecology 39 227-237 1997年

    DOI: 10.1007/BF02765269  

  136. he effect of ecological and genetic neighborhood size on the evolution of two competing species 査読有り

    Kawata, M

    Evolutionary Ecology 10 609-630 1996年

  137. Effective population size in a continuously distributed population 査読有り

    M Kawata

    EVOLUTION 49 (6) 1046-1054 1995年12月

    出版者・発行元:SOC STUDY EVOLUTION

    ISSN:0014-3820

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    An individual-based simulation model was created to examine genetic variability, time until fixation and spatial genetic structure in a continuously distributed population. Previous mathematical models for continuously distributed populations have the difficulty that the assumption of independent reproduction and independent dispersal of offspring cause clumped spatial distribution and thus violate an assumption of random spatial distribution. In this study, this problem is avoided by considering the dispersal behavior of offspring. The simulation results showed that the inbreeding effective population size estimated by the rate of decrease of heterozygosity during the first 15 generations corresponds to the neighborhood size calculated by the standard deviation of the dispersal distance (sigma(T)). This inbreeding effective population size does not greatly change with the area of simulation when the densities and sigma(T) are the same. However, the inbreeding effective population size estimated by heterozygosity using the first 500 generations is larger than the neighborhood size calculated by the dispersal distance and increases with the area of simulation with the same densities. The variance effective population size, estimated by time until fixation of alleles, increases with dispersal distance (sigma(T)) and with the area of simulation given the same densities. The inbreeding effective population size and variance effective population size were smaller than the actual population size unless sigma(T) is sufficiently large (2 sigma(T) &gt; approximate L/2, where L is a side of the simulation square).

  138. The effect of color polymorphism on mortality in the aphid Macrosiphoniella yomogicola 招待有り 査読有り

    Hiroko Agawa, Masakado Kawata

    Ecological Research 10 (3) 301-306 1995年12月

    出版者・発行元:Springer-Verlag

    DOI: 10.1007/BF02347856  

    ISSN:0912-3814 1440-1703

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    We examined body color polymorphism in the aphid Macrosiphoniella yomogicola from July to September 1993. We classified body color into eight types: green 1, green 2, red 1, red 2, white, orange, yellow and mist. The frequencies of body color varied with time and among patches of the host plant, yomogi (Artemisia spp.). Color diversity within a shoot was calculated using the Shannon diversity index. Of five usable data sets, three showed negative relationships between color diversity and mortality. The regression coefficients for two of these relationships were significant. No significant relationship between mortality and the number of aphids was found. The color diversity was not significantly related to a particular body color found on a yomogi shoot. Color polymorphism may be maintained because selection may favor a high color diversity on the host plant shoot. © 1995 Ecological Society of Japan.

  139. Emergent and effective properties in ecology and evolution 査読有り

    Masakado Kawata

    Researches on Population Ecology 37 (1) 93-96 1995年6月

    出版者・発行元:Springer-Verlag

    DOI: 10.1007/BF02515765  

    ISSN:0034-5466 1438-390X

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    Emergent properties are often discussed in arguments concerning relationships among different levels. However, the different definitions of emergent properties sometimes confuse the arguments about macro-level phenomena, since some authors regard emergent properties not only as observable global patterns but as properties that affect and cause change in ecological and evolutionary processes. Thus it is important to distinguish higher-level or larger-scale properties that can influence particular ecological and evolutionary processes from those that cannot. I call the former properties effective properties. I gave examples that show why the distinctions between effective and non-effective properties are important. © 1995 Society of Population ecology.

  140. A comment on "Can Group-functional behaviors evolved by cultural group selection?" 招待有り 査読有り

    Masakado Kawata

    Current Anthropology 36 484-485 1995年6月

  141. From Artificial individuals to global patterns 査読有り

    KAWATA Masakado

    Trends in Ecology and Evolution 11 417-421 1994年

  142. RELATIVE IMPORTANCE OF DIRECT AND INDIRECT INTERACTION AMONG INDIVIDUAL SNAILS 査読有り

    M KAWATA

    RESEARCHES ON POPULATION ECOLOGY 35 (1) 69-77 1993年6月

    出版者・発行元:SOC POPULATION ECOLOGY

    DOI: 10.1007/BF02515646  

    ISSN:0034-5466

    詳細を見る 詳細を閉じる

    Individual organisms interact directly through behavior, and indirectly through resource consumption and environment modification. The effects of different kinds of interactions on individual growth and reproduction will differ. Freshwater snails may interact directly for food resources and indirectly through substances dissolved in water. I separated the effects of the direct behavioral interaction and indirect interaction through waters using laboratory experiments with freshwater snails Physa acuta. Behavioral direct interaction have negative effects on the growth, but indirect interaction through water environments has positive effect on the growth. The importance of distinction of different kinds of interactions were discussed.

  143. The effects of visual donsity on fecundity in guppy 査読有り

    「Nishibori, M, 「M. Kawata」

    Environmental Biology of Fishes 37 213-217 1993年3月

  144. The Growth of juvenile snails in water conditioned by snails of a different spectes 査読有り

    KAWATA Masakado

    Oecologia 91 75-79 1992年

  145. Individual differences in food access in freshwater snails, Physa acuta 査読有り

    「Kawata, M」「Inaba, M

    Journal of Ethology 10 75-79 1992年

  146. FLUCTUATING POPULATIONS AND KIN INTERACTION IN MAMMALS 査読有り

    M KAWATA

    TRENDS IN ECOLOGY & EVOLUTION 5 (1) 17-20 1990年1月

    出版者・発行元:ELSEVIER SCI LTD

    ISSN:0169-5347

  147. Kin interaction and population growth: reply 査読有り

    Kawata, M

    Trends in Ecology and Evolution 54 371-372 1990年

  148. Social Organization of the Vole Clethrionomys rufocanus and Its Demographic and Genetic Consequences 招待有り 査読有り

    Ishibashi, Y. Saitho, T, Kawata, M

    Researches on Population Ecology 40 39--50 1989年6月

    DOI: 10.1007/BF02765220  

  149. GROWTH AND DISPERSAL TIMING IN MALE RED-BACKED VOLES CLETHRIONOMYS RUFOCANUS-BEDFORDIAE 査読有り

    M KAWATA

    OIKOS 54 (2) 220-226 1989年2月

    出版者・発行元:MUNKSGAARD INT PUBL LTD

    ISSN:0030-1299

  150. Mating success, spatial organization and male characters in the field experimental populations of the red-backed vole 査読有り

    KAWATA Masakado

    Journal of Animal Ecology 57 217-235 1988年

  151. The effect of introduced males on spatial pattern of initially introduced red-backed voles 査読有り

    「Kawata, M, Saitoh, T

    Acta Theriologica 33 585-588 1988年

  152. Units and passages: A view for evolutionary biology and ecology 査読有り

    Masakado Kawata

    Biology and Philosophy 2 (4) 415-434 1987年10月

    出版者・発行元:Kluwer Academic Publishers

    DOI: 10.1007/BF00127699  

    ISSN:0169-3867 1572-8404

    詳細を見る 詳細を閉じる

    Many authors, including paleobiologists, cladists and so on, adopt a nested hierarchical viewpoint to examine the relationships among different levels of biological organization. Furthermore, species are often considered to be unique entities in functioning evolutionary processes and one of the individuals forming a nested hierarchy. I have attempted to show that such a hierarchical view is inadequate in evolutionary biology. We should define units depending on what we are trying to explain. Units that play an important role in evolution and ecology do not necessarily form a nested hierarchy. Also the relationships among genealogies at different levels are not simply nested. I have attempted to distinguish the different characteristics of passages when they are used for different purposes of explanation. In my analysis, species and monophyletic taxa cannot be uniquely defined as single units that function in ecological and evolutionary processes. The view discussed in this paper may provide a more general basis for testing competing theories in evolution, and provide new insights for future empirical studies. © 1987 D. Reidel Publishing Company.

  153. The effect of kinship on spacing among female red-backed voles, Clethrionomys rufocanus bedfordiae 査読有り

    Kawata, M

    Oecologia 72 89-97 1987年

  154. Pregnancy failure and suppression by female-female interaction in the field population of the red-backed vole, Clethrionomys rufocanus bedfordiae 査読有り

    Kawata, M

    Behavioral Ecology and Sociobiology 20 89-97 1987年

  155. Mating System and reproductive sucess in a spring population of the ren-backed vole 査読有り

    KAWATA Masakado

    Oikos 45 115-122 1985年

  156. SEX-DIFFERENCES IN THE SPATIAL-DISTRIBUTION OF GENOTYPES IN THE RED-BACKED VOLE, CLETHRIONOMYS-RUFOCANUS-BEDFORDIAE 査読有り

    M KAWATA

    JOURNAL OF MAMMALOGY 66 (2) 384-387 1985年

    出版者・発行元:AMER SOC MAMMALOGISTS

    ISSN:0022-2372

  157. Protein polymorphisms and their genetic control in the red-backed vole, Clethrionomys rufocanus bedfordiae 査読有り

    「Kawata, M, 「, J. Ueda」

    Animal Brood Groups and Biochemical Genetics 15 146-150 1984年10月

︎全件表示 ︎最初の5件までを表示

MISC 17

  1. 外洋性渦鞭毛藻Ornithocercus magnificusに見られる共生シアノバクテリアのゲノム解析

    中山卓郎, 高野義人, 野村真未, 柴小菊, 稲葉一男, 谷藤吾朗, 河田雅圭, 稲垣祐司

    藻類 66 (1) 73 2018年3月10日

    ISSN:0038-1578

  2. Evolutionary genetic basis underlying social and cognitive abilities in human

    Daiki Sato, Takashi Makino, Masakado Kawata

    GENES & GENETIC SYSTEMS 91 (6) 343-343 2016年12月

    出版者・発行元:GENETICS SOC JAPAN

    ISSN:1341-7568

    eISSN:1880-5779

  3. Spectral sensitivity of guppy visual pigments reconstituted in vitro to resolve association of opsins with cone cell types

    Shoji Kawamura, Satosi Kasagi, Daisuke Kasai, Ayumi Tezuka, Ayako Shoji, Akiyoshi Takahashi, Hiroo Imai, Masakado Kawata

    GENES & GENETIC SYSTEMS 91 (6) 376-376 2016年12月

    出版者・発行元:GENETICS SOC JAPAN

    ISSN:1341-7568

    eISSN:1880-5779

  4. Gustatory receptor gene repertoires linked to host range variation in Nymphalid butterflies

    Hiromu Suzuki, Katsuhisa Ozaki, Takashi Makino, Hironobu Uchiyama, Shunsuke Yajima, Masakado Kawata

    CHEMICAL SENSES 41 (9) E228-E229 2016年11月

    出版者・発行元:OXFORD UNIV PRESS

    ISSN:0379-864X

    eISSN:1464-3553

  5. 小笠原諸島に侵入したグリーンアノールの進化的変化の検出と集団ゲノム解析

    玉手智史, 森英章, COMPOSANO Brian J., LKRYSKO Kenneth, 舟山亮, 中山啓子, 牧野能士, 河田雅圭

    日本生態学会大会講演要旨(Web) 63rd 2016年

  6. 沖縄の移入グッピー集団における色覚の遺伝的分化

    酒井祐輔, 稲田垂穂, 青木翔子, 鶴井香織, 満行知花, 陶山佳久, 辻和希, 河田雅圭

    日本進化学会大会プログラム・講演要旨集(Web) 18th 2016年

  7. 小笠原諸島に侵入したグリーンアノールの進化的変化の検出と集団ゲノミクス解析

    玉手智史, 森英章, KRYSKO Kenneth L., 牧野能士, 河田雅圭

    日本進化学会大会プログラム・講演要旨集(Web) 17th 2015年

  8. ゲノム内の遺伝子重複の進化がもたらす生物の適応力

    河田雅圭, 牧野能士

    化学と生物 53 (11) 731-733 2015年

    出版者・発行元:公益社団法人 日本農芸化学会

    DOI: 10.1271/kagakutoseibutsu.53.731  

  9. 小笠原諸島に侵入したグリーンアノールの進化的変化の検出

    玉手智史, 牧野能士, 森英章, KRYSKO Kenneth L., 河田雅圭

    日本生態学会大会講演要旨(Web) 61st 2014年

  10. The neo-sex-chromosome formation drove the evolution of protein-coding sequences and transcriptome in three-spine sticklebacks

    Kohta Yoshida, Takashi Makino, Katsushi Yamaguchi, Shuji Shigenobu, Mitsuyasu Hasebe, Masakado Kawata, Atsushi Toyoda, Asao Fujiyama, Jun Kitano

    GENES & GENETIC SYSTEMS 88 (6) 356-356 2013年12月

    出版者・発行元:GENETICS SOC JAPAN

    ISSN:1341-7568

    eISSN:1880-5779

  11. 個体の分散が生物多様性の進化に与える効果

    河田雅圭

    日本生態学会誌 54 (3) 255-257 2004年4月

    出版者・発行元:一般社団法人 日本生態学会

    DOI: 10.18960/seitai.54.3_255  

    ISSN:0021-5007

  12. The evolution of extreme shell shape variation in the land snail Ainohelix editha: a phylogeny and hybrid zone analysis (vol 12, pg 1869, 2003)

    H Teshima, A Davison, Y Kuwahara, J Yokoyama, S Chiba, T Fukuda, H Ogimura, M Kawata

    MOLECULAR ECOLOGY 12 (11) 3199-3199 2003年11月

    出版者・発行元:BLACKWELL PUBLISHING LTD

    DOI: 10.1046/j.1365-294X.2003.02017.x  

    ISSN:0962-1083

  13. Evolution of biodiversity through divergent processes: Theories and facts - I. Theories

    Masakado Kawata

    Population Ecology 44 (2) 49-50 2002年8月

    DOI: 10.1007/s101440200006  

    ISSN:1438-3896

  14. 進化論再考-未解決問題の解明に向けて

    河田雅圭

    イミダス 261-27 2002年1月

    出版者・発行元:集英社

  15. 絶滅パターンの原因と進化.

    河田雅圭, 千葉聡

    科学 64 684-690 1994年10月

  16. Reply from Masakado Kawata

    Masakado Kawata

    Trends in Ecology and Evolution 5 (11) 371-372 1990年

    DOI: 10.1016/0169-5347(90)90099-Y  

    ISSN:0169-5347

  17. Imperial Japan [3]

    Masakado Kawata, Eiich Kasuya

    Nature 338 (6214) 370 1989年

    DOI: 10.1038/338370c0  

    ISSN:0028-0836

︎全件表示 ︎最初の5件までを表示

書籍等出版物 13

  1. 個性学入門 : 個性創発の科学

    保前, 文高, 大隅, 典子

    朝倉書店 2021年8月

    ISBN: 9784254102956

  2. 多様性と異文化理解

    河田雅圭

    東北大学出版会 2021年3月

  3. 生物多様性は復興にどんな役割を果たしたか-東日本大震災からのグリーン復興

    中静透, 河田雅圭, 今井麻希子, 岸上祐子

    昭和堂 2018年11月

    ISBN: 9784812217344

  4. 生態適応科学:自然のしくみを活かし、持続可能な未来を拓く

    東北大学生態適応グローバルCOE編

    日経BP社 2013年2月

    ISBN: 9784822208691

    詳細を見る 詳細を閉じる

    以下から無料ダウンロード可能 https://ochotona0.wixsite.com/mysite/tekioukagaku

  5. エコゲノミクス―遺伝子からみた適応―

    北野潤, 河田雅圭

    共立出版 2012年12月

  6. Encyclopedia of Islands

    「Echenique-Díaz L. M.」「 J. Yokoyama」「M. Kawata」

    University of California Press 2009年9月

  7. シリーズ群集生態学(2) 進化生物学からせまる

    河田雅圭, 千葉聡

    京都大学学術出版会 2009年3月

  8. シリーズ進化学 行動・生態の進化

    河田雅圭

    岩波書店 2007年7月

  9. Macroecology: Concept and Consequences

    「Butlin,R.」「J. Bridle」「M. Kawata」

    Blackwell 2003年7月

  10. シリーズ性を問う1. 原理論

    河田雅圭

    専修大学出版会 1997年

  11. 講座進化第1巻

    河田雅圭

    東京大学出版会 1991年

  12. はじめての進化論

    河田雅圭

    講談社 1990年10月

  13. 進化論の見方

    河田雅圭

    紀伊国屋書店 1989年8月

︎全件表示 ︎最初の5件までを表示

講演・口頭発表等 18

  1. A genetically explicit model of speciation by sensory drive within a continuous population 国際会議

    Ayako Shoji, Shoji Kawamura, Ole Seehausen

    Japanese-Korean Joint Meeting for Mathematical Biology 2006年9月16日

  2. CO2噴出地におけるオオバコの進化:遺伝子流動と局所適応

    中村伊都, 横山潤, 彦坂幸毅

    第53回生態学会大会 2006年3月

  3. Speciation by sensory drive through the evolution of visual pigments along an environmental light gradient 国際会議

    Spatial Heterogeneity in Biotic and Abiotic Environment: Effects on Species Ranges, Co-evolution, and Speciation 2006年2月6日

  4. Adaptive radiation

    第7回日本進化学会大会 2005年8月

  5. シクリッドにおいて同所的種分化は起こりうるのか?

    河田雅圭

    第52回生態学会大会 2005年3月

  6. 性選択による種分化機構;理論的検討

    河田雅圭

    日本遺伝学会 第76回大会 2004年9月27日

  7. 分散の進化と生物多様性

    第51回 日本生態学会大会 2004年8月27日

  8. 生物間相互作用から見た生物多様性の進化

    第6回日本進化学会大会 2004年8月

  9. Mechanical and behavioral reproductive isolation in Carabid beetles 国際会議

    Kawata, M

    The First Okazaki Biology Conference 2004年1月25日

  10. The evolution of visual pigments and premating isolation: a theoretical consideration 国際会議

    Kawata, M, Shoji, A, Kawamura S

    Cichild Symposium 2003. Evoluton, Diversification and speciation 2003年9月20日

  11. 交配後隔離に関わる遺伝子の有害性と種分化

    河田雅圭, 林岳彦

    第5回日本進化学会 2003年8月19日

  12. The effects of individual dispersal on the evolution of niche width and the patterns of biological diversity

    河田雅圭

    第50回日本生態学会 2003年3月19日

  13. Isolation and migration in island population of Hipposideros turpis (Chiroptera, Hipposideridae): History or current patterns? 国際会議

    Echenique-Diaz LM, Yokoyama J, Ishibashi Y, Kawata M

    VIII INTECOL 2002年8月

  14. 性選択による交配前隔離の進化:分子機構と生態的要因

    河田雅圭

    第4回日本進化学会大会 2002年8月

  15. Genetics and the boundaries of species distributions

    R. Butlin, J. Bridle, M. Kawata

    2002 Annual Symposium;Macroecology: reconciling divergent perspectives on large scale ecological 2002年4月

  16. 生物多様性の進化のしくみをさぐる

    河田雅圭

    第49回日本生態学会大会公開講演会 2002年3月30日

  17. 環境変動と密度依存性の進化

    河田雅圭, 澤田寛, 横山潤

    第49回日本生態学会大会 2002年3月

  18. Theoretical and empirical problems in postmating isolaton 国際会議

    T. Hayashi, M. Kawata

    The 20 th symposium of the Society of Population Ecology 2001年10月

︎全件表示 ︎最初の5件までを表示

共同研究・競争的資金等の研究課題 43

  1. Does Evolution Repeat Itself? Genome Evolution and Phenotypic Convergence in Island Lizards

    提供機関:International Human Frontier Science Program organization

    研究種目:Research Grant

    2020年12月 ~ 2025年11月

  2. Small ミトコンドリアRNAによるヒト集団の進化

    河田 雅圭, POZZI ANDREA

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for JSPS Fellows

    研究機関:Tohoku University

    2021年7月28日 ~ 2024年3月31日

  3. グッピーにおける色彩装飾形質の進化:csf1r遺伝子に着目して

    河田 雅圭

    2021年4月 ~ 2024年3月

  4. アノールトカゲを用いた温度ニッチシフトの進化機構の解明

    河田 雅圭, 赤司 寛志, 牧野 能士

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))

    研究機関:Tohoku University

    2019年10月7日 ~ 2023年3月31日

    詳細を見る 詳細を閉じる

    本年度は、キューバ自然史博物館のLuis Cadiz博士らと共同で、6種のキューバアノールトカゲにおいて決定した全ゲノム配列を用いて、温度適応に関わるゲノムの特徴の解析を行った。ゲノム内容をアメリカ本土のアノールトカゲのものと比較し、アノールトカゲの多様化の過程で出現・蓄積された遺伝的変異を推定した。遺伝子重複解析の結果、重複する遺伝子の割合が高温開環境と相関している可能性が示唆された。さらに、過去の有効人口を推定した結果、それぞれの種の人口規模がキューバの地史に影響された可能性が示唆された。また、これまでの研究で、TRPA1が温度感知に関与しており、Anolis allogus TRPA1の活性化温度はA. homolechisやA. sagreiよりも低いことを明らかにした。そこで、Georgia大学のMenke博士と共同で、TRPA1のCRISPR/Cas9による遺伝子編集実験の計画を検討した。またTRPA1と行動的熱感受性の関係の一般性を調べるため、TRPA1と行動的熱反応に関するメタ解析を行ったところ、多様な外温動物種で一貫した関係が見られた。このような温度感受性の違いは、トカゲの生息地の分化に重要な役割を果たすと考えられるが、生息地の分化に関わる分子基盤は不明であった。そこで、Tulane大学のGunderson博士との共同で、これまで行ったキューバのアノールトカゲに加えて、プエルトリコのアノールトカゲ(A. cristatellusとA. krugi)でRNA-seqを行い、温度感受性遺伝子を解析した。後者2種は、A. allogusと同様に比較的涼しい場所に生息している。その結果、860個の遺伝子の発現レベルが種間で有意に異なることが示され、6個の遺伝子が特に発現変動遺伝子として重要であると検出された。

  5. 日本列島人で交雑後特異的に適応進化した精神的特性・食物に関連する遺伝子の検出

    河田 雅圭

    2019年4月1日 ~ 2021年3月31日

    詳細を見る 詳細を閉じる

    縄文人ゲノム34個体、中国古代人ゲノム47個体(Yang at al., 2020とNing at al., 2020による北東アジア由来で約1万~3000年のゲノム配列)を用いて、現代日本人集団との比較を行った。各集団のアレル頻度をSNP座位を含むリードのカウントを使用して、最尤推定した (Mathieson et al., 2015)。日本人集団と分化している領域を検出するため、 (1)現代日本と縄文人間、(2)現代日本と古代中国人間について、FSTを領域ごとに計算し、その値が大きい上位0.1%以上を分化している領域として検出した。日本と縄文間で分化している遺伝子として2型糖尿病(SNHG17、NAMPT、ACAD10) や肥満(ATXN2)などエネルギー代謝や糖質代謝に関わる遺伝子や、心疾患(TEX41)が検出された。また、アルコール代謝に関わるALDH2, 耳垢(ABCC11)や乳がん(CYP1B1、ACBB11)などが検出された。ALDH2、ABCC11、CYP1B1は、現代日本人のゲノム配列から選択的一掃などを検出する方法で自然選択を受けた遺伝子としても検出されている(Okada et al. 2018, Yoshimura et al. 2006, Yasumizu et al. 2020)。2型糖尿病や肥満などに関わる遺伝子は、稲作伝来による食生活の変化が影響していることが考えられた。日本と古代中国人で分化している遺伝子として、統合失調症(GRIK1、THEM4、RP4-598G3.1)、アルコール代謝(ADH cluster)、前立腺癌(HDAC1)、膀胱癌(EDC3)、身長(DOCKK3)などが検出された。ADH clusterは、自然選択を受けた遺伝子としても検出されている(Yasumizu et al. 2020)。

  6. VMAT1変異が精神的個性に及ぼす影響:マルチスケールアプローチによる解明

    河田 雅圭

    2019年4月1日 ~ 2021年3月31日

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    申請者らはこれまで、小胞モノアミントランスポーター1(VMAT1)遺伝子において、ヒト系統特異的に出現したアミノ酸置換(136Asn→Thr/Ile)が自然選択を受けてきたことを示した。また、培養細胞を用いたVMAT1タンパク質の機能解析により、この置換がVMAT1の神経伝達物質の取り込み能力に影響することを示している。一方で、ヒト特異的なVMAT1遺伝子変異が関連遺伝子群の発現や脳内の神経活動、そして個体の行動に与える包括的な影響は不明であった。これらを解明するため、本研究では当該の1アミノ酸置換を施した遺伝子編集マウスを作製し、網羅的な行動バッテリーテスト、関連脳部位における脳波測定、および関連遺伝子の脳内発現量測定を実施した。 行動実験の結果、136Ile型マウスは野生型(Asn型)あるいはThr型マウスに比べて、不安様行動が少ないほか、社会性行動に変化が見られた。また、高架式十字迷路試験を実行中のマウスの脳内に電極を挿入し、開放・閉鎖アーム滞在時における神経活動を測定した。不安傾向に差が見られたことをふまえ、背内側前頭前皮質および扁桃体の神経活動に着目したところ、他の遺伝子型に比べて、136Ile型マウスは扁桃体の神経活動に違いが見られた。さらに、各遺伝子型4個体の前頭前皮質、扁桃体、線条体を用いて、網羅的な遺伝子発現解析(RNA-seq)を行なった。その結果、136Ile型マウスは野生型マウスに比べて、扁桃体において神経伝達に関わる遺伝子群の発現が低下していることが明らかとなった。これらの結果は、これまで中枢神経系での役割があまり解明されていなかったVMAT1遺伝子の作用機序を新たに示す研究成果であるといえる。また、人類進化の観点からも、VMAT1遺伝子がヒトの情動進化に果たした役割を実験的に明らかにした重要な成果であると考えられる。

  7. 雌によって選好されるゲノム領域の特定:環境依存的優良遺伝子化説の検証に向けて

    河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2018年4月1日 ~ 2021年3月31日

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    グッピーは、個体ごとにオスの体色および、それを基準としたメスの配偶者選好性に著しい多様性が維持されている。本研究では、野外集団において、交配前および交配後の雌の選好性によって選択されたオスのゲノム領域を特定することを目的とした。解析の結果、各集団で402~434個の候補遺伝子が検出された。候補遺伝子の中には、シグナル形質(体色・鰭)や生存力(免疫・抗酸化)に関する遺伝子がいくつか検出された。免疫および抗酸化に関わる遺伝子は、子どもの生存率向上に関わるgood geneの可能性がある。本研究によりメスの配偶者選好性の進化に関わった可能性のある候補遺伝子を得ることができた。

  8. モデル線虫近縁種による大きな進化的変化機構の解明と進化実験モデル生物の確立

    河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Research (Exploratory)

    研究機関:Tohoku University

    2018年6月29日 ~ 2020年3月31日

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    本研究では、転位因子が大きな進化的な変化をもたらしたという仮説を検証するために、C. elegans の近縁種で体サイズが大きく変化したC. inopinataに着目した。ゲノム中に転位因子由来の配列と判定された配列は、C. elegansで12%、C. inopinataで25%であった。解析の結果、C. inopinataに転位因子がある遺伝子群は、C. inopinataにおいてもC. elegansにおいても発現量が有意に低い傾向にあり、C. inopinataの転位因子は二種の共通祖先で既に発現量が低い遺伝子近傍に挿入している可能性が示された。

  9. VMAT1変異と体験が情動の個性に及ぼす影響:マルチスケールアプローチによる解明

    河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    研究機関:Tohoku University

    2017年4月1日 ~ 2019年3月31日

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    培養細胞を用いて、VMAT1遺伝子の進化がタンパク質の機能に与えた影響を調べた。各遺伝子型のVMAT1の神経伝達物質の取り込みを蛍光顕微鏡で観察した結果、130Glu/136Asnや130Glu/136Thr、130Gly/136Ileの神経伝達物質の取り込み効率が高かった一方で、130Gly/136Asnおよび130Gly/136Thrの取り込み効率は低かった。これは、Glu130Glyの変化がVMAT1の神経伝達物質の取り込みを抑制し、Thr136Ileは促進することを示している。また、これらの遺伝子型の進化過程をふまえると、人類進化の初期段階ではモノアミンの取り込みが減少したと考えられ、モノアミン取り込み効率の低い136Thrが現代人集団において強い神経質傾向やうつ傾向と関連していることを考慮すると、チンパンジーとの共通祖先からの分岐以降、人類進化の初期段階においては不安や神経質傾向に対して強い正の選択圧が働いていた可能性が考えられた。また、 東北メディカル・メガバンク機構(ToMMo)の大規模コホートデータを用いて、VMAT1遺伝子に働く平衡選択メカニズムの解明を目指した。ToMMoの約7000-9000人分の精神傾向に関わる質問票およびVMAT1遺伝子型データを用いて、一般化線形モデルで解析したところ、Thr型とうつ傾向との関連が示された。また、VMAT1遺伝子型と性別、そして周囲の人々とのつながりの交互作用がうつ傾向に影響を与えることが示された。さらに、ヘテロ型では将来に対する積極性および適応度(子供の数と婚姻経験の有無をもとに変数を作成)が高い傾向が見られた。このように、遺伝子型が表現型に与える影響が状況によって異なること、そして平均してヘテロ型の適応度が高いことが、VMAT1遺伝子多型の維持に働いていると考えられた。

  10. キューバのアノールトカゲで複数回進化した開放高温環境への適応進化仮説の検討

    河田 雅圭, 牧野 能士, 丸山 真一朗, 寺井 洋平

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2016年4月1日 ~ 2019年3月31日

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    本研究では、キューバに生息するアノールトカゲの系統関係から、独立に4回、森林低温環境から開放高温環境へ進化したと推定され、高温放環境に生息する2種について、正の自然選択を受けた遺伝子を推定した。その結果、コラーゲン産生に関わるtgfb1の配列が進化していることがわかった。また、A. allogusおよびA. sagreiについて全ゲノム配列決定を行った。ゲノム全体での重複遺伝子率は、A. sagrei(81.0%)がA. allogus(45.4%)に比べて高い値を示した。このことは、高温開放環境への適応に遺伝子重複が重要であることを示唆している。

  11. 体サイズの進化に伴って変化する性質と独立な性質:遺伝子改変線虫を用いて

    河田 雅圭, 杉本 亜砂子, 牧野 能士, 丸山 真一朗, 横山 潤

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2016年4月1日 ~ 2018年3月31日

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    近年発見されたC. elegans の姉妹種であるC. inopinataを用いて、体長の進化に寄与した遺伝子を特定することを目的とした。二種間で大きな体長の差が生じるL4幼虫期と成虫期で、発現パターンが、種間で異なる遺伝子として2699遺伝子が検出された。6種の線虫のうち、C. inopinataの系統でのみ正の選択圧が42の遺伝子で検出され、その中に、daf-2があった。daf-2は細胞膜で発現するインスリン受容体で、C. elegansの変異体は体サイズが大きくなることが知られ、daf-2遺伝子の進化が体サイズの進化に対して大きな影響をもつ可能性が示唆された。

  12. グッピーにおける雌配偶者選好性の個体間変異と可塑性の進化機構の解明

    河田 雅圭, 牧野 能士, 河村 正二, 狩野 賢司

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2015年4月1日 ~ 2018年3月31日

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    グッピーを用いて、成育時の光環境とカロテノイドの影響に焦点を当て、遺伝子型の変異とDNAメチル化によるエピジェネティックな変異が雄の体色に対する雌の配偶者選好性の個体間変異に与える影響を調べた。オプシン遺伝子の発現量は、光感受性と雄体色に対する雌の選好性に影響し、その発現量は、成育時の光環境とオプシン遺伝子LWS-1の遺伝子型との交互作用によって影響されることがわかった。またオプシン遺伝子の発現量の遺伝子と環境との交互作用は、DNAメチル化率によるものと示唆された。βカロテン高摂取により、目では、光順応に関する遺伝子が、脳では、神経伝達に関係する遺伝子においてDNAメチル化が増加した。

  13. 視覚の適応が創出する種の多様性

    寺井 洋平, 河田 雅圭, 大田 竜也, 今井 啓雄, 藤村 衡至

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (C)

    研究機関:The Graduate University for Advanced Studies

    2014年4月1日 ~ 2017年3月31日

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    本研究ではお生態適応による種分化機構の生物多様性の創出における一般性を明らかにすることを本研究の目的としている。本研究は3つの研究から構成されるが、1)アノールの研究では環境光、婚姻色を呈した皮膚の反射光、視物質の吸収から、環境適応による種分化が示唆された。2) ノトセニアの研究からは視覚の環境への適応が示された。3)シクリッドの研究からは視覚に関する遺伝子が環境適応のために自然選択で、婚姻色形成に関する遺伝子が配偶者選択により性選択で進化し種分化を起こしてきたことを示し、生態適応による種分化の機構の一般性を示した。

  14. 遺伝子重複と生物の適応力の進化;酵母の進化実験系の確立による検証

    河田 雅圭, 牧野 能士

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2014年4月1日 ~ 2016年3月31日

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    予測できない変動環境が遺伝子の重複を増加させ、保持し、そのような変動環境下で進化したゲノムは、適応力や進化可能性が高いという仮説を検証するために、出芽酵母(Saccharomyces cerevisiae)を用いて、変動環境下で進化させ、全ゲノム配列をモニタリングする進化実験を行った。進化実験終了後の解析の結果、RAD27変異株では3種の不規則変動環境条件と高負荷の6環境をランダム変動させる条件において、最適一定環境条件と比較して新規重複領域数が有意に増加した。また、450世代から500世代までの平均適応度は、RAD27変異株において、新規重複領域数が多いほど適応度が高い傾向を示した。

  15. 全ゲノム重複後に消失する遺伝子パターンの実験的検証

    牧野 能士, 守屋 央朗, 河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2014年4月1日 ~ 2016年3月31日

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    本研究では世代時間が短く扱いやすい4倍体酵母を用いた進化実験系を確立し、全ゲノムが倍加後も機能的遺伝子クラスターが保持されつつ、大規模遺伝子消失が起きるかを検証した。4倍体酵母を紫外線照射しながら200日間培養した結果、ゲノム中に多くの突然変異が検出された。これら突然変異のうち有害変異が機能的遺伝子クラスター上にどのように分布しているかを調査した結果、同一染色体上の遺伝子クラスターで同時に有害変異が生じていることが明らかとなった。このことは、倍数化後に遺伝子がランダムに消失していくのではなく、機能遺伝子クラスターが保持されるよう選択が働いている事を示している。

  16. 新たな気候帯への適応進化機構の解明:半砂漠地帯のキューバアノールトカゲを用いて

    河田 雅圭, 牧野 能士, 田村 宏治, 瀧本 岳, 長太 伸章

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2013年4月1日 ~ 2016年3月31日

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    走行力測定による温度耐性実験の結果、森林集団のA. homolechisは30度に比べ35度で最高走行速度が低下したのに対し、半砂漠集団のA. homolechisは、走行速度が低下しなかった。RAD-seqにより検出されたSNPでの遺伝的構造解析では、2つの集団間に違いが観察された。LOSITANによる自然選択を受けている領域の検出では5つのSNPを検出した。33度および36度の温度環境で5日間飼育したのち脳を抽出し、RNA-seq解析を行い発現変動遺伝子の検出を行った。33度および36度で発現量が有意に異なった遺伝子は、森林集団のA. homolechisで78、半砂漠集団で43であった。

  17. 外来種の侵略性に関る遺伝的基盤の解明

    牧野 能士, 河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2013年4月1日 ~ 2016年3月31日

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    生物が持つ適応力は種によって異なる。本研究は、重複遺伝子保持率から生物が持つ環境適応力を予測する手法の確立を目指し、動物ゲノムの重複遺伝子保持率と生態的特徴の関係を調査した。本研究で侵略的外来種アメリカザリガニの全ゲノム配列決定し、本種を加えたゲノム配列既知の動物を対象にした比較ゲノム解析により、侵略的外来種の重複遺伝子保持率が高いことを明らかにした。重複遺伝子保持率と環境適応力との関連を強く支持するものであり、ゲノム配列情報からの環境適応力評価への応用が期待される。

  18. 複合適応形質進化の遺伝子基盤解明

    長谷部 光泰, 倉谷 滋, 嶋田 透, 藤原 晴彦, 川口 正代司, 深津 武馬, 西山 智明, 岡田 典弘, 阿形 清和, 河田 雅圭, 郷 通子, 豊田 敦, 藤山 秋佐夫, 望月 敦史, 矢原 徹一

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    研究機関:National Institute for Basic Biology

    2010年4月1日 ~ 2016年3月31日

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    本領域の目的である、多様な研究から「複合適応形質進化の共通メカニズム」を推定するという総合的研究を展開する、進化生物学とゲノム生物学を融合させる、を実現するため総括班を有機的に組織し、下記の活動を行い、効率的に連携できた。(1)領域会議を年2回、インフォマティクス情報交換会を5年で18回、ニュースレターを5年で63号発行し、領域内での情報共有、共通意識形成を行った。(2)ゲノム支援活動として実験方法のアドバイス、ゲノム配列決定支援、外部委託についてのアドバイス、各班のインフォマティクス担当者などに指導を行った。(3)形質転換実験技術支援を行った。(4)国内、国際シンポジウムをほぼ毎年開催した。

  19. 分布停滞および拡大に関わる進化的要因:チョウ類を用いての検証

    河田 雅圭, 横山 潤, 牧野 能士, 長太 伸章

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2012年4月1日 ~ 2015年3月31日

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    地球温暖化による気温の上昇とともに多くの種が分布北限を北上させていることが報告されているが、北上せず停滞していたり、逆に縮小している種も多く存在する。本研究では東北地方に分布北限があるチョウのうち、この数十年分布を大きく北上させている4種と、分布が停滞している3種を用い、遺伝的集団構造をゲノムワイドなSNPを用いて解明した。その結果、停滞している3種は地域集団間での分化を伴う遺伝的集団構造がみられたが、拡大している4種ではみられなかった。分布域の拡大が停滞している種は温度以外の要因に局所適応しているために、北上させることが困難であると示唆された。

  20. 遺伝子コピー数変異の野外集団解析による新たな疾病生態学の開拓

    河田 雅圭, 牧野 能士

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2012年4月1日 ~ 2014年3月31日

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    ヤマアカガエルの抗菌ペプチドのコピー数変異のゲノムでの重複の状態を調べるため、フォスミドライブラリーを作成し、抗菌ペプチドを含むクローンの配列を十世代シークエンサーでの決定を試みた。次世代シークエンサーで解読したリードを複数のアセンブラでアセンブルした結果、約40kbpの配列のうち33kbはtemporinを含まない非コード領域で、残りの配列の中に、temporin-1Ojと1Ocを含む少なくとも3コピーの配列があることが明らかになった。今回得られたコンティグの情報では、temporin-1O遺伝子の詳細のゲノム上の位置を断定することはできなかった。

  21. キューバにおけるアノールトカゲの適応形質部位特定とその候補遺伝子探索

    河田 雅圭, 牧野 能士, 北野 潤, 田村 宏治, 瀧本 岳, 北野 潤, 田村 宏治

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2010年 ~ 2012年

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    本研究で、同所的に生息するTrunk-Ground型(幹から地面に生息する)の種数は、異なる温度環境場所に生息できる種数とその地域で何種が種分化によって起源しているかによって決まっていることを明らかにした。また、後肢長の長いTrunk-Ground型のA.sagreiと短いTwig型のA.angusticepsの間では、発生の複数の段階で後肢長に違いが生じることを明らかにし、今後の遺伝的解析の基盤を得た。

  22. 侵入外来種の侵入・定着時の進化的応答の検出:全ゲノム配列決定によるアプローチ

    河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2010年 ~ 2011年

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    1965年に小笠原諸島に侵入し、侵略外来種となっているグリーンアノール(Anolis calorlinensis)が、40年以上の間で、どのような進化をしたかを調べるため、小笠原父島の16個体、移入元であるフロリダの8個体を次世代シークエンサーSOLiDを使って、全ゲノム解読を行った。読まれた断片の配列を、データベース上にある配列2. 0. 61を使用して、アセンブルを行った。現在、アセンブルが終了し、染色体LGbとLGhの塩基多様度の違いを調べた。その結果、父島集団の個体が塩基多様度が大きいことが明らかになった。

  23. グッピーの色覚多型の維持機構の解明:雄体色と雌選好性多型と関連づけて

    河田 雅圭, 河村 正二

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2009年 ~ 2011年

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    TrinidadとTobagoの野外13集団において、LWS遺伝子の4遺伝子座、SWS1, RH1遺伝子座、比較参照遺伝子として、核DNAの8領域の配列を決定した。その結果、LWS遺伝子のFSTの値は、参照DNAに比べて有意に大きく、集団によって異なるDivergent Selectionが働きLWS遺伝子の異なる配列が維持されている可能性が示された。また、LWS2の配列変異が、オプシン遺伝子の発現量の変異に影響し、それが光感受性に関係していることを明らかにした。

  24. "未来の生態系"天然二酸化炭素噴出地における植物の適応プロセスの解明

    彦坂 幸毅, 河田 雅圭

    2007年 ~ 2009年

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    丹生CO2噴出地由来のオオバコから自殖種子を得て、実験圃場のオープントップチャンバーを用いて競争実験を行った。この競争実験では、高CO2領域由来の個体と低CO2領域由来の個体を隣接させ、どちらが個体サイズや種子繁殖量を多くすることができるかを解析した。低CO2条件では両者に有意な違いは認められなかったが、高CO2条件では低CO2由来の個体のほうが多く種子を残すという結果が得られた。本研究で用いた条件では高CO2由来の個体が高CO2条件で適応的であるとの証拠は得られなかった。 さらに、青森県湯ノ川、山形県朝日鉱泉、富山県林道の高・低CO2領域からオオバコ種子を採取し、実験圃場のオープントップチャンバーにて成長実験を行っている。月に一度刈り取りを行い、個体重・窒素量の測定及び光合成測定を行う予定であるが、実験は継続中であり結果はまだ出ていない。 このほか、高CO2環境下での群落のCO2収支の研究を行い、論文を投稿した。これは現在Plant Ecology誌に受理見込みである。さらにCO2噴出地の植物を用いた研究の論文をいくつか投稿中である。

  25. 地球・地域環境変化と生物進化:ミジンコ休眠卵を用いた分子古生物学的解析

    占部 城太郎, 河田 雅圭, 横山 潤, 上田 眞吾, 小田 寛貴

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:Tohoku University

    2007年 ~ 2009年

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    調査を行った山形県畑谷大沼では、複数のミジンコ種が雑種を形成し長期間個体群を維持していること、さらに、1970年代のオオクチバス侵入と同時に別種のDaphnia pulexも定着するようになったことを、古生物学的及び分子生物学的手法により明らかにした。一方、八幡平高山湖沼では大気降下物由来と考えられる富栄養化が過去30年の間に生じていること、それに伴って新種を含む動物プランクトンも個体数を増大させていることを明らかにした。

  26. グッピーの色覚に影響する視物質遺伝子の多様性:雌の配偶者選好の変異と関連づけて

    河田 雅圭, 河村 正二, 横山 潤, 河村 正二, 横山 潤

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2006年 ~ 2008年

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    本研究では、グッピー(Poecilia reticulata)の赤型オプシン遺伝子の維持気候の解明に向けて研究を行った。この研究によってグッピーの視物質遺伝子をすべて同定し、LWS-B, C. D以外の吸収波長を特定した。さらに、沖縄に生息する移入個体を用いて、光感受性を調べる行動実験を行い、LWS-BとLWS-Cから同定できる遺伝子型の違いが緑波長領域の感受性の違いに影響を与えていることが示された。また、グッピー原産地のトリニダッド2集団の個体をLWS-BとLWS-Aの配列を決定し、集団遺伝的解析を行った、Aripo川下流の集団でLWS-Bに関して平衡選択の可能性が示唆された。

  27. 個体の移動分散が資源利用の進化と種多様性に及ぼす影響:理論予測と島群集による検証

    河田 雅圭, 千葉 聡, 横山 潤

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2003年 ~ 2005年

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    ニッチ分割が多様性パターンへ与える影響を検出するためには、(1)質の違う資源がある。(2)種によって利用資源が異なる。(3)資源の分布パターンが種の多様性パターンに影響を与える、という仮定が全て確かめられる必要があると考えられる。これら全てを満たした上で、資源分布が多様性パターンに及ぼす効果を検出した研究はこれまで行われてこなかった。本研究では、浦戸諸島(馬放島、朴島、桂島、野々島、寒風沢島)におけるチョウのサンプリング調査及び植生調査を基に、チョウ群集の多様性パターンと、各種が利用する餌資源の空間分布との関係を解析し、ニッチが多様性パターンに与える影響を検証した。 解析の結果、多様性パターンと資源分布パターンの間に強い有意な相関が見られ、多様性パターンと距離、資源分布パターンと距離には相関が見られなかった。Hubbleの中立理論では、個体の移入率が非常に重要となるため、群集間の距離が多様性パターンに強い効果をもつことになる。一方でニッチ理論に従うならば、多様性パターンは資源の分布パターンと共に変化するはずである。しかし、一般的に距離と資源分布パターンの間には相関があることが多い。そこで両者に相関が無い状態で、二つの理論の重要性を比較検証する必要がある。今回の結果では、資源分布パターンと距離に相関は認められなかった。また、多様性パターンと資源分布パターンの間に相関が見られ、特に島を分割した場合に有意な相関関係が得られたことから、浦戸諸島において、資源分布パターンが多様性パターンに強く影響していることが強く示された。

  28. 多様性の揺籠:フロンティア環境における生物進化

    千葉 聡, 加瀬 友喜, 河田 雅圭, 山崎 和仁

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2003年 ~ 2005年

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    適応放散の生態的、遺伝学的プロセスを明らかにするため、小笠原諸島の陸生貝類カタマイマイ属を用いて、種間の生態的、遺伝的性質の分化の様子、および種内での生息場所、形態的な分化の様相を調査した。その結果生態的分化による種分化のため、いったん分化した種が後に生活場所を変化させ、結果的に他種の生活場所と同じになったため、繁殖隔離が消失し雑種化がおきる、というケースが観察された。このように、一時的な種が認められたことは、急速な適応放散の過程が現在も進行中であることを示している。さらにこのような雑種化によって、どちらの親種とも異なる全く新しい形態をもつ集団が出現することがわかった。適応放散の過程では、雑種化が新しい表現型の進化に大きな役割を果たしているのかもしれない。 ミトコンドリアDNAを用いて、本土のマイマイ属全種の系統推定を行った。系統解析の結果、関東-東北地方に分布するマイマイ属陸貝では、隆起や海水順変動、氷期の寒冷化などに伴う集団の縮小、拡大、さらに供給地からの繰り返し移住により、著しく複雑な遺伝的変異の構造が成立したことが明らかになった。 異質な環境の接点である潮間帯の巻貝ホソウミニナと吸虫類寄生虫(Trematoda)の関係に注目し、ミトコンドリアDNAおよび核遺伝子(ITS遺伝子)の分析を行なったところ、吸虫類寄生虫に多数の同胞種が存在することがわかった。またこれらの吸虫類の多くは、遺伝的変異に明瞭な地理的構造を示さなかった。一方、ホソウミニナは地域ごとに異なる遺伝的変異を持ち、地域間で遺伝子流動が阻害され隔離が進んでいることがわかった。これはホストと寄生虫で分散様式が全く異なることを反映していると考えられる。寄生虫では地理的隔離よりもホストのシフトによる同所的種分化のほうが起こりやすいと考えられる。

  29. ホタルのルーツを求めた中国雲南省の発光甲虫生態調査

    近江谷 克裕, 藤森 一浩, 大場 信義, 河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:National Institute of Advanced Industrial Science and Technology

    2002年 ~ 2005年

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    ホタルを代表とする発光甲虫は世界的に分散拡散する典型的な生物で、進化分散を考える上で貴重な研究対象である。これは発光という生理現象が、比較的新しい時代に獲得した形質であることから、発光生物を探ることは、今、生息する生物群の拡散を知る上で重要であると考えられるからである。本研究では、ホタルのルーツの一つの候補として中国雲南省地域を注目し、中国雲南省の現地調査を行った。平成14年9月に中国雲南省昆明周辺、平成15年12月に中国雲南省昆明南部、平成16年1月にブラジルサンバウロ周辺、平成16年6月は雲南省南西部ラオス国境付近、平成17年6月は雲南省シーサーパンナ地方からミャンマー国境付近の南部地方の調査研究を行った。その結果、ゲンジ、ヘイケボタルの近縁種と思われる半水棲ホタルを発見した。これは水棲ホタルの進化、拡散を考える上で重要な新規な知見である。また、イリオモテボタル近縁種の採取に成功、採取サンプルより抽出したミトコンドリアDNAの全遺伝子配列を決定、分子レベルでイリオモテボタルとの相関を検討した。その結果、生息環境が異なり、出現時期等も異なるが、遺伝子レベルで高い相同性を示すことが明らかになった。これは、日本とユーラシア大陸の生物群の分散を考える上で、貴重な知見である。これ以外にも日本産ホタル群と類似性の高い10数種のホタルを発見した。一方、ブラジルではヒカリコメツキムシを採取、採取サンプルより抽出したミトコンドリアDNAの全遺伝子配列を決定した。ヒカリコメツキムシは発光甲虫群の地球レベルでの進化、分散を考察できるユニークな生物であることが明らかになった。

  30. 空間行動と共存群集の進化:C.elegansをつかった実験進化生態学の開拓

    河田 雅圭, 横山 潤

    2002年 ~ 2003年

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    本年度の研究で以下の成果を得た (1)大腸菌のパッチによる空間構造の変化、卵植え継ぎによる経代実験の確率、GFPによる遺伝型の計測など、C.elegansによる進化実験系を確立した。 (2)17のストレインについて、増殖率、分散率などを調べた。また、密度依存増殖、密度依存分散についても基礎データを得た。多くのストレインではパッチから別のパッチに移動する分散率は低く、0.2以下であるが、いくつかのストレインで高い分散率を示すものがあった。これは主に、餌感知などに関わる突然変異個体であった。また、GFPを導入した野生型ストレインで密度依存分散の行動に異常がみられ、GFPの挿入された部位がこの行動に関係しているものと予測された (3)空間構造のある条件とない条件で、密度依存分散をする低分散型と密度依存分散をしない高分散型ストレインを競争させたところ、通常、空間構造がある条件では高分散が選択されるが、密度依存分散をする低分散型ストレインが10世代後に増加し、密度依存分散が空間構造のある条件で重要なことが示された (4)空間構造のある条件とない条件で、低分散型・低増殖率と高分散型・高増殖率のストレインを競争させた。通常、パッチが飽和環境にある場合は、空間構造がなし条件で低分散型ストレインが増加することが予測されたが、実験では、空間構造があるなしにかかわらず、高分散型・高増殖率が増加した。線虫では、分散率と増殖率の間でトレード・オフはみられず、パッチに侵入してからの増殖率が競争において重要であることが示された。

  31. 個体をベースとした生物多様性のためのデータベースシステムの開発および構築と運用

    河田 雅圭, 粕谷 英一, 早瀬 敏幸, 横山 潤, 平山 義治, 三中 信宏, 平山 善治

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2001年 ~ 2003年

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    我々は、生物多様性を登録するための新たなシステム,NoCodeを提唱し、それに基づき、データベースシステムを構築している、データベースシステムの改良、および新たな機能の追加を行い、Nocode Database ver 0.2を構築し、試用運行の段階まで到達した。 これまでの多様性データベースは種をベースとして登録、記録が行われるために、生態学進化生物学、保全生物学的な解析には適していない。そこで、本データベースは属性を原初概念とする計算法による個体データベースを実現したものである。本システムは、発展リレーショナルモデルをもとに設計開発を行った。本データベースの特徴は、登録は個体単位で行われ、個体の特性をレコードとして随時追加、登録できる。また、個体を登録するにあたり、登録すべき特性を検索、また追加などが可能である。昨年度からシステムの改良を行い、現在、ログイン、ユーザー管理機能、メニュー、フォーム管理、フォームの編集、フォームを用いた新規個体データの追加、フォームを用いた個体データの検索、個体データの編集を行えるように開発した。 また、本システムの試用運行のために、陸産巻き貝とマルハナバチをモデルにデータベースの試用入力を行った。 このシステムによって、生物の登録を個体ベースで柔軟に行うことが可能になり、個体の特性による検索などが可能になり分類名にこだわらない検索をすることができる。また、位置データをGISなどと連動させることにより、生物保全に役立てることができると期待できる.

  32. 生息地の構造と密度依存的性質の進化:個体数変動の進化的意義と関連させて

    河田 雅圭, 嶋田 正和, 横山 潤, 千葉 聡

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2000年 ~ 2002年

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    生息地の空間構造の変化が、個体数動態や進化的変化に大きな影響を及ぼすことは知られている。しかし、多くの研究は、空間構造としてメタ個体群を仮定し、メタ集団間の移住の程度が生態的・進化的動態におよぼす影響について考察されてきた。しかし、環境の変化が空間構造自体を変化させるという状況も考えられる。たとえば、通常は隔離された水たまりあるいは小さな池が、大雨などによりときおり一つの大きな池となり、大きなランダム交配集団になるという状況がある。 小集団内で成長、繁殖し、その後、個体が分散し、一つの大きなデームを形成するようなalternative mixing population(AMP)において、小集団に隔離されたとき、密度依存的に繁殖を抑制せず、早く成長し、繁殖をした個体は、大きな集団になったときに、より多くの個体で占めることが可能になる。一方、密度依存的に繁殖、成長を抑制した個体は、大きな繁殖集団になったとき、その頻度を減らすを予測される。 本研究では、このような密度依存的成長および繁殖の違いが生息地の空間構造に違いによって引き起こされるという仮説を検証するために、2つの異なる空間構造を示す生息地において、それぞれの生息地からPhysa acutaを採集し、マイクロサテライトDNAを調べ、集団の空間の遺伝的構造を調べた結果、一つの集団は、ランダムな交配集団(RP)で、一方の集団はAMPであることが推測された。そして、AMPの個体は、正の密度依存成長を示し、より早期に繁殖をしたのに対し、RMでは負の密度依存成長を示し、後期に繁殖をした。これらの結果は、上記の仮説を支持するものであった。

  33. 海から陸への進化:巻貝の上陸過程とその要因

    千葉 聡, 河田 雅圭, 加瀬 友喜

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:TOHOKU UNIVERSITY

    2000年 ~ 2002年

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    核28SrRNA遺伝子に基づき、アマオブネ超科の系統推定を行った。得られた系統関係と化石に基づく系統関係から、このグループでは、異なる系統で繰り返し異なる時代に、海から陸への進出が起きたことが推定された。現在、陸上生活をしているグループは、その共通祖先とは全く異なる形態をしており、上陸に伴い急激な進化が起きたことが推定される。そしてそれらとの共通祖先は、現在は淡水域または海域の洞窟中で、隠棲的な生活をしていることがわかった。 潮間帯最上部に生息するホソウミニナとウミニナを材料とし、野外における移植実験や生息範囲の比較を通して、これらの種間関係の解明を試みた。ホソウミニナでは,上部に殻の形態が大きく異なる個体が分布していた。予察的な採餌行動の調査を行ったところ、これらの個体は常に上部で採餌、休眠しており、より下部に生息する個体とは住み場所や環境の干出度に対する好みに、明らかな違いが認められた。これらのタイプ間の遺伝的構成の違いを調べるため、ミトコンドリアCOI遺伝子と酵素多型の分析を行ったところ、mtDNAには差が見られなかったが、酵素多型には遺伝子頻度に上下で有意な差が認められた。このことは、潮間帯の帯状分布が種間相互作用とは無関係に、種内競争を経た同所的種分化により生じる可能性を示す。そして、巻貝の上陸が同所的種分化により起こりうる可能性を示唆する。 陸貝ではミトコンドリアDNAの分子進化速度が海産巻貝より著しく速い(10-20倍)ことがわかり、また集団内で極端に多様な遺伝的変異が存在していることが判った。また同様な陸域での海域より著しく速い進化速度が核28SrRNAでも見られた。

  34. 種分化のメカニズム

    吉村 仁, 千葉 聡, 河田 雅圭, 長谷川 孝博

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (C)

    研究機関:Shizuoka University

    1999年 ~ 2002年

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    本研究の目的は、生物の種多様性を創生する唯一の方途である種分化がどのような条件で起こりうるかを検証することである。この種分化のメカニズムに関する検証をシミュレーションによる理論的研究と化石や分子系統による実証的研究の二つのアプローチから行った。 特に、基本的な個体ベースモデルを作成して、性淘汰が種分化を引き起こすか、そしてその起こりやすさは性淘汰における形質分布とどのように関係しているかを検証した。その結果、従来のように生態学的地位(ニッチェ)の相違がなくても、メスの配偶者選択に起因する性淘汰のみで種分化が起こりうること、そして、個体群が分断隔離され配偶者選択にかかるオスの形質の変異が大きくなるにつれ、種分化の可能性が大きくなることを見出した。これは、種分化が、従来のように生態学的地位によって制限されたものでなく、無限に起こる可能性をしめしている。 この結果は、驚異的な種多様性を誇る一部の生物群集、たとえば、熱帯多雨林やアフリカ湖沼におけるシクリッド魚の群集のような群集が頻繁な種分化により可能になったことを示した。 このほか以下のように、この理論・モデルをもとに生物多様性・交尾繁殖行動に関する各種の理論・モデルを構築・解析した。(1)種分化が地理的な空間的配置・分布が氷河期などの環境変動を通して多種化を引き起こす大域的モデル、(2)分化した種の共存安定の仕組みに関する考察としての多種共存安定の格子モデル(草本群落)、(3)昆虫にみられる山頂集中行動の個体ベース交尾行動モデルのシミュレーション、(4)動物の性比の季節変異や安定性の定量的解析などである。

  35. 種分化による多様性創出のメカニズムの解明

    河田 雅圭, 横山 潤, 牧 雅之, 千葉 聡, 久保田 耕平, 曽田 貞滋

    2000年 ~ 2000年

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    生殖隔離がどのようなメカニズムで進化したかという問題の解明は、地球上での多様性創出の原因を考える上でも重要なテーマの一つである。この問題を「種分化のメカニズムの解明」と「種分化と生物の多様性の関係」から探る研究を押し進めるために、2回の会合を東北大学(仙台)で開催した(11月と2月)。会合では、植物、動物、微生物の対象生物について、理論的研究、分子生物学的研究、生態学的研究、生物地理学的研究、古生物学的研究について討論が行われた。討論の結果、種分化メカニズムの解明のための研究には、(1)交配や資源利用にかかわる遺伝メカニズムを分子レベルで解明する必要性であること、(2)自然界での多様性のプロセスを解明するためには、グローバルな視点からの多様性のパターンの解析が必要であり、そのためには個体をベースとたデータベースが必要であるということ、(3)どのように生態的な要因が種分化の促進に関わっているかを実証研究すること、(4)実際の生物に応用できる理論的研究の発展がのぞましいこと、などが確認された。 また、今後の新たな研究計画に利用できるように、種分化研究の文献データベースの作成や一部計測データのデータベースの作成を行った。今回の成果は、日本生態学会でのシンポジウム「生物多様性の進化機構の解明」などで公開されるほか、雑誌での特集記事として企画している。また、継続的に論議し、今後、大きなプロジェクト研究として計画予定である。

  36. 生息地の空間構造が有害遺伝子の蓄積に及ぼす影響:淡水産巻き貝を用いての検証

    河田 雅圭, 舘田 英典

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (C)

    研究機関:TOHOKU UNIVERSITY

    1998年 ~ 1999年

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    生息地の空間構造が有害遺伝子の蓄積に及ぼす影響を、サカマキガイ(Physa acuta)を使った研究とシミュレーションモデルを使った予測を用いて調べた。2つの異なる生息地から貝を採集した; (1)水田で水のあるときは比較的水位の安定した大きな集団(Large stable population)、(2)遊水池の水たまりで通常は小さな水たまりであるが、雨によって大きな池となってつながる(Alternate mixing population). Altenate mixing populationでは、小さな水たまりの小集団内で高密度で近親交配をしている可能性が高く、そのため高密度での近親交配で適応度の低下した個体は淘汰されるため、高密度下での近交弱勢の効果は小さいと予測できる。それを確かめるため、2つの集団から採集した個体の近交弱勢の程度を低密度と高密度の状態で調べた。産卵数に関してはAltenate mixing populationの個体は高密度で近交弱勢はほとんど見られなかった。しかし、生存率に関しては、Altenate mixing populationの個体の方が低密度高密度ともに近交弱勢の効果が大きかった。卵数と生存率を考慮した適応度に関しては、高密度ではAltenate mixing populationの個体の近交弱勢が低く、低密度ではLarge stablepopulationの近交弱勢の程度が低かった。この結果は、はじめの予測を支持するものであった。また、生息地の空間構造が弱有害遺伝子の蓄積に与える影響についてシミュレーションモデルで確かめた。その結果、突然変異荷重には、全体の個体数だけでなく、neighborhood sizeが独立に影響していることが明らかになった。また、生息地の形が有意に突然変異荷重に影響し、特に細長い地形は有害遺伝子の蓄積の効果が高く、絶滅率を高めることが明らかになった。

  37. 局所的相互作用がもたらす生物集団の動態と多義性

    河田 雅圭, 原 登志彦

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (C)

    1996年 ~ 1997年

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    本研究では、淡水産巻き貝と付着藻類をもちいて、それぞれの空間分布と局所的な相互作用が、巻き貝の成長や空間分布、また藻類の空間的な生物量の動態にどのように影響しているかを特定することを目的とした。実験的に貝と藻類の相互作用系を設定し、画像解析の方法により、藻類の空間分布と定量化を行った。これらの結果に対して、Geostatisticsなどの」統計的解析を行い藻類分布の空間構造を解析するとともに、個体ペースモデルによるシミュレーション解析を行い、集団のダイナミクスに影響する要因を特定した。実験の結果、藻類の成長量は、おなじ空間(格子)内の藻類量はマイナスの密度依存効果があるが、隣接空間の藻類量は、プラスの影響があることが明らかになった。また、藻類の空間分布は、貝のグレージングがない状況では、パッチなど空間構造をつくらないか、めだたないパッチをつくった。貝のグレージング圧が高いほど、そのパッチ構造は明瞭になり、時にはより大きなパッチを形成した。この実験結果の要因を解析するために30x30の格子モデルによるシミュレーションを行った。その結果、隣接空間の藻類量が当核空間の藻類量にプラスの効果があるとき、ゆるやかなパッチ構造をつくった。これは、貝がいな以上体でパッチをつくる要因であると考えられる。さらに、一度グレージングをしたパッチに再び貝がグレージングをする率が高いほどより大きなパッチをつくり、また、一度グレージングをしていないパッチをグレージングする率が有る程度低いときによりパッチは明瞭になった。グレージング圧は、ある程度高いときにもっともパッチは鮮明になるが、低くても高くてもパッチは不鮮明になった。貝が多いほどパッチが大きく、鮮明になるという傾向から、貝が、同じ場所をグレージングする傾向があることを示唆している。このような貝と藻類、藻類どうしの相互作用が不均一な藻類の空間構造をつくりだしていると考えられた。

  38. 生態的に安定な種の組み合わせに関する実験的・理論的研究

    藤井 宏一, 徳永 幸彦, 河田 雅圭

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:The University of Tsukuba

    1995年 ~ 1997年

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    1980年代後半から脚光を浴び始めてきた個体モデルや人工生命の手法は,個々の生物現象に注目し,ボトムアップにシステムを構築していく手法であり・微分方程式などで記述される力学系モデルによる解析よりも,現実の生態系を考察するにはより相応しい方法であると考えられる.本研究は,これまでの実験的研究に基づいて,個体モデル,あるいは人工生命モデルを構築し,ボトムアップ的に種の多様性と安定性の関係について考察しようとするものである.また,このように構築されたモデルの挙動を,実験的に実際に構築された生態系と照らし合わせて評価しようとするものである.我々は当該研究期間に,一方で豆-豆象虫-寄生蜂を用いた実験系における系の複雑性-安定性の問題を研究し,他方で人工生命の生態学への利用を通じて,生態学的に安定な種の組み合わせの可能性について研究した. 過去3年間,恒温室で,豆-豆象虫-豆象虫に捕食寄生する寄生蜂(各々複数種)でなる実験生態系を構築し,飼育した.一方,同期間にシミュレーションモデルを構築し,段階的により大規模でかつ一般的な生態系モデルへと拡張し,人工生命的手法を用いた生態系モデルを構築し,その挙動を調べた. 生態的に安定な種の組み合わせを形成する構成種を生成するメカニズムとしては,可変長遺伝的アルゴリズムなどの手法を用い,最終年度には,各栄養段階を特徴づけるビッ列で表現される人工生命を生成し,有限の資源を巡る競争や捕食関係をモデル内で進化させてみた.これらのシミュレーションの結果に見られる種の組み合わせを,実験的研究の成果と対比しながら,進化的に安定な種の組み合わせという概念の有効性について考察を行なった.

  39. 人間行動と進化

    長谷川 寿一, 河田 雅圭, 長谷川 真理子, 安藤 清志, 中村 真, 山岸 俊男

    1996年 ~ 1996年

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    本研究は、人間行動の進化に関心をもつ進化生物学者と、進化理論が人間理解にどのように貢献するかに関心をもつ人文社会学者が、同じテーブルについて双方の主張に耳を傾け、広く人間研究全般と進化学的分析の関連について学際的な議論を交わす目的で企画された。全体会議「人間性の進化的理解」は、1996年11月30日と12月1日の2日間にわたって東京で開催され、研究代表者分担者14名、招待講演者3名、その他オブザーバーを含めて約35名が参加した。発表内容としては、人文社会系研究者から、歴史学研究(古代ローマの嬰児遺棄と奴隷制)、文学研究(英詩における制約条件の解析)、倫理学研究(倫理と進化的基盤)、経済学研究(経済学における進化的アプローチの可能性)、社会心理学研究(信頼、公正感の進化的背景と文化的変容)、発達心理学研究(人における育児戦略)が、また進化生物学者から、性淘汰の理論、社会生物学の社会的受容過程が、それぞれ問題提起され、指定討論者を中心に議論が交わされた。初日の討議は深夜にまで及び、また翌日は早朝から議論が再開されるなど、専門領域の壁を感じさせないきわめて活発な意見交換が続いた。この会議からだけでも、人間研究を学際統合的に理解する上で、進化的アプローチが非常に重要なものであることが再認識された。また、本研究を主体としたワークショップや講演が、日本心理学会(立教大)や動物心理学会(東大)で行われた。本研究の成果の一部は、「科学」の1997年4月号の特集「人間の心の進化」に掲載予定である。

  40. 集団の進化を創出するマクロレベルとミクロレベルの相互作用の検出

    河田 雅圭

    1996年 ~ 1996年

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    進化のプロセスにおける集団選択の重要性はこれまで多く論争されてきた。多くの集団選択のモデルは集団の間の移動や分散が小さいほど集団選択が効果的であると結論している。しかし、個体の分散距離や移住は同時に多くの要因(集団間の遺伝的変異、絶滅率、集団生成率、局所的密度制御など)に影響する。これらの要因は同時異なる影響を集団選択の有効性に与える。数理モデルでは、これらの要因を独立のパラメタとして用い、しばしば、はじめにこれらの異なるパラメタの関係を仮定していた。しかし、これらは多くの要因の間の相互作用から生じる現象である。そこで、本研究では、個体の繁殖と分散のみを仮定した人工生命シミュレーションを行った。その人工生命モデルでは、絶滅、個体群サイズ。集団間の遺伝的変異、集団の生成等の集団の減少は個体の繁殖と分散の結果として現れる。利他行動に影響する遺伝子座をもつ人工生命個体を、13のパッチ上の環境でシミュレートした。個体の繁殖は、まわりの利他行動をする個体の数とまわりの個体数によって決定される。子どもは親から標準偏差σ_d、平均0の正規乱数で決定した。結果は、利他行動をする遺伝子が広がる確率は、分散距離がσ_d=50までのとき次第に増加し、その後分散距離が増加するにしたがって、減少した。このことは、利他行動遺伝が広がる確率は分散距離がある程度低い時に最大になるが、それ以下の低いときには減少することがわかった。この結果は、利他行動遺伝子の頻度の低い集団での高い絶滅率と利他個体の高い移住率という集団選択の2つの要因、から説明できるかもしれない。集団の絶滅と生成という要因による集団選択だけでは利他行動遺伝子の進化は説明できないかもしれない。しかし、この研究は、ある程度の分散による効果が、集団選択による利他行動遺伝子の進化が可能であることを示した。

  41. 個体の行動と進化を創り出すマクロレベルとミクロレベルの相互作用の検出

    河田 雅圭

    1995年 ~ 1995年

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    本年度の研究では、個体の相互作用と分散のパターンによって空間構造がどう変化し、それによりどのような進化(遺伝子頻度の変化)が生じるかを解析し、これまでの進化理論(たとえば連続集団上での遺伝子頻度の変化モデル、集団選択モデル、血縁選択モデル)の予測と対比した。これまでの理論では個体の相互作用と移動分散(局所的相互作用)とグローバルな特性(空間構造、絶滅や再移住)を独立のパラメータとおいていた。しかし、現実には、局所的相互作用とグローバル特性の間には創発的な関係がある。そこで、個体の相互作用と繁殖、移動分散のルールを仮定し、空間構造などのグローバル特性は個体の繁殖と移動の結果であるという人工生命モデルを作成し、今回は特に集団選択のモデルについて検討した。これまでのモデルでは、創発的なレベル間の関係を仮定していなかったため、個体の分散距離が小さくなると遺伝子頻度の局所的な違いが増大し、集団選択の効果が大きくなると考えられていた。しかし、個体の分散の現象にともなって、局所的な密度の増加と再移住率の低下による遺伝子流入の低下が同時おこることになり、個体の分散距離が少なすぎても集団選択の効果が減少することが判明した。このことは、個体の移動や分散と局所的な相互作用が重要と考えられるプロセスでは、これまでの単純な集団遺伝モデルは適用できず、個体レベルと集団レベルとの複雑な創発的関係を考慮した人工生命シミュレーションが重要であると示唆された。今後は、本年度の研究をさらにすすめると同時に、扱う集団を群集レベルまでに拡張して行う予定である。さらに、プログラムを実行中にさまざまなデータを記録するという方法でレベル間のフィードバックの詳しいメカニズムを明らかにする予定である。

  42. 個体間の相互作用と個体の空間分布の相互影響

    河田 雅圭

    1994年 ~ 1994年

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    本研究は、2つの効果(資源の空間分布が個体の相互作用にあたえる影響と個体の相互作用が資源の空間分布にあたえる影響)の相互影響を調べることが目的である。本年度は特に、資源の空間分布が個体の行動と相互佐用に及ぼす影響を調べるために実験を行った。実験は、寒天で培養した藻類を異なる空間分布で配置し(ランダム、集中、一様)、サカマキガイの行動をビデオで5日間記録した。最適採餌理論によると、個体の餌場所の滞在時間は、集中分布のとき最も長く餌に滞在し、一様分布のときもっとも短いと予測される。しかし、実際には、ランダム分布のときにもっとも長い滞在時間を示した。しかし、より小さなスケールでみると、餌場が近くに位置するときは頻繁に餌場間も移動していることが観察された。このことは、サカマキガイは、近隣の餌の分布は認識して採餌しているが、大きなスケールでの餌の分布を認識していないことを示している。Y字間による実験(一方に藻類をおき、貝がどちらに接近するかを調べる実験)によっても、サカマキガイは、約2.5cm以内に餌場しか認識出来ないことが示された。 複数個体をつかった相互作用の実験では、他個体が餌場に存在すると、餌場にアプローチしないことが多く、合計の餌場滞在時間は個体の間で大きな差がみられるようになった。直接的な個体間の接触は少ないことから、粘液やその他の物質を介して、お互いにさけあってるのかもしれない。 以上のような実験から、貝の採餌行動は、餌の空間分布に影響をうけるが、その空間分布のスケールによって影響がことなること、さらに他個体の採餌行動の影響を強く受けることがわかった。

  43. 資源の空間的分布と個体間の相互作用

    河田 雅圭

    1993年 ~ 1993年

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    1)画像解析による藻類量の定量 画像解析による藻類がどの程度行えるかをしらべるために、実験的にプラスチック板に付着させた藻類を画像解析と乾燥重量によって測定した。その結果、有意な回帰が存在し、画像解析により、藻類量が定量かできることが判明した。 2)藻類量と2種巻貝の相互作用 実験的に、2種の淡水性巻貝(サカマキガイとハブタイモノアラガイ)を互いに水を通じて間接的に相互作用できるように設定した実験容器を野外の池に入れ1カ月間、藻類量の変化と貝の成長、繁殖を調べた。その結果(1)サカマキガイはハブタイモノアラガイの間接的な影響で、成長が促進されが、ハブタイモノアラガイはサカマキガイの影響を受けなかった。(2)サカマキガイの個体数は藻類量と有意な相関があった。(3)藻類量は、サカマキガイの個体数とハブタイモノアラガイの個体数さらに、ハブタイモノアラガイがサカマキガイに及ぼす間接的効果によって影響されることが明らかになった。 今後、この実験をふまえて、よりミクロな空間的な藻類の分布と淡水性巻貝同士の相互作用との関係について調べていく予定である。

︎全件表示 ︎最初の5件までを表示

メディア報道 4

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    2005年4月

    メディア報道種別: 新聞・雑誌

  4. テクノギャラリ-、生物はなぜ多様に進化したのか?

    スカイパーフェクTV:サイエンスチャンネル

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    メディア報道種別: テレビ・ラジオ番組

その他 12

  1. 浦戸諸島「里島・里海グリーン復興プロジェクト」

    詳細を見る 詳細を閉じる

    浦戸諸島における里島・里海グリーン復興の推進について

  2. 生物間相互作用に着目した高山・亜高山生態系の脆弱性評価システムの構築に関する研究

    詳細を見る 詳細を閉じる

    温暖化にともなう山岳生態系の脆弱性評価

  3. Evolution of opsin genes in guppies

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    Evolution of opsin genes in guppies

  4. Evolution of adaptive radiation

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    Evolution of adaptive radiation

  5. Speciation of cichlid fishes

    詳細を見る 詳細を閉じる

    Speciation of cichlid fishes

  6. Evolution for the next generation

  7. グッピーの視覚遺伝子の多様性

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    グッピーの視覚遺伝子の多様性

  8. 新石垣空港建設予定地周辺の洞窟における集団遺伝学的研究

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    新石垣空港建設予定地周辺の洞窟における集団遺伝学的研究

  9. Genetics and the boundaries of species

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    Genetics and the boundaries of species

  10. 新石垣空港建設予定地周辺の洞窟に生息するカグラコウモリの集団遺伝学的研究

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    新石垣空港建設予定地周辺の洞窟に生息するカグラコウモリの集団遺伝学的研究

  11. Population Ecology, Editorial Boad

  12. Journal of Ethology, Editorial Boad

︎全件表示 ︎最初の5件までを表示