2022/01/19 更新

写真a

カツハラ コウキ
勝原 光希
KATSUHARA Koki
所属
環境生命科学学域 助教
職名
助教

学位

  • 博士(理学) ( 2020年3月   神戸大学 )

研究キーワード

  • ツユクサ

  • 送粉

  • 植物の繁殖様式

  • 多種共存機構

研究分野

  • ライフサイエンス / 生態学、環境学

  • 環境・農学 / 自然共生システム

  • ライフサイエンス / 進化生物学

経歴

  • 岡山大学   学術研究院環境生命科学学域   助教

    2021年4月 - 現在

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  • 岡山大学   日本学術振興会特別研究員PD

    2020年4月 - 2021年3月

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  • 神戸大学   日本学術振興会特別研究員DC1

    2017年4月 - 2020年3月

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論文

  • Intersexual flower differences in an andromonoecious species: small pollen-rich staminate flowers under resource limitation

    K. Murakami, K. R. Katsuhara, A. Ushimaru

    PLANT BIOLOGY   2022年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Andromonoecy, the presence of perfect and staminate flowers in the same individual, has evolved repeatedly in angiosperms. The staminate flowers are generally smaller than the perfect flowers in species that produce staminate flowers plastically when resources are limited. The smaller staminate flowers are expected to be less attractive to pollinators and have reduced size-matching with pollinators than perfect flowers. We hypothesized that these potential disadvantages of staminate versus perfect flowers facilitate the evolution of sex-specific floral morphology, such as allometric relationship between flower size and male reproductive organ. We compared six floral morphology traits, pollen production, pollinator visits and pollen removal from anthers between staminate and perfect flowers in several natural Commelina communis populations. Nectarless and zygomorphic C. communis flowers have polymorphic stamens with attracting, feeding and pollinating anthers and were visited by diverse pollinators. Staminate flowers were significantly smaller than perfect flowers, despite a large overlap in size between sexes. The lengths of pollinating stamens did not differ between staminate and perfect flowers, and staminate flowers produced significantly more pollen. We observed significantly more pollinator visits to perfect flowers than to staminate flowers. By contrast, pollen removal from pollinating stamens was significantly higher in staminate flowers than in perfect flowers. There is sexual dimorphism in flower morphology in C. communis. Staminate flowers with smaller attraction organs, similar pollinating stamens and higher pollen production assure higher pollen donor success relative to perfect flowers. Our results suggest that the morphological changes in staminate flowers enhance pollination success, even with limited resources.

    DOI: 10.1111/plb.13383

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  • The eco-evolutionary dynamics of prior selfing rates promote coexistence without niche partitioning under conditions of reproductive interference

    Koki R. Katsuhara, Yuuya Tachiki, Ryosuke Iritani, Atushi Ushimaru

    JOURNAL OF ECOLOGY   109 ( 11 )   3916 - 3928   2021年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Pollinator-mediated reproductive interference can occur when two or more plant species share the same pollinators. Recent studies have suggested that prior autonomous selfing mitigates reproductive interference, potentially facilitating coexistence even in the absence of pollination niche partitioning (i.e. the pre-emptive selfing hypothesis). However, whether the evolution of prior selfing promotes coexistence, in the context of the eco-evolutionary dynamics of population size, selfing rates and inbreeding depression, remains poorly understood. We constructed an individual-based model to examine the conditions under which the evolution of prior selfing promotes coexistence in the context of mutual reproductive interference. In the model, two plant species compete by way of mutual reproductive interference, and both have the potential to evolve the capacity for prior autonomous selfing. We expected that purging of deleterious mutations might result in evolutionary rescue, assuming that the strength of inbreeding depression declines as the population selfing rate increases; this would enable inferior competitors to maintain population density through the evolution of prior selfing. Our simulation demonstrated that evolution of prior selfing may promote coexistence, whereas reproductive interference in the absence of such evolution results in competitive exclusion. We found that lower pollinator availability is likely to favour rapid evolutionary shifts to higher prior selfing rates, thereby neutralising the negative effects of reproductive interference in both species. When the strength of inbreeding depression decreased with an increase in the population-level selfing rate, moderate pollinator availability resulted in long-term coexistence in which relative abundance-dependent selection on the prior selfing rate served to intermittently maintain the population density of the inferior competitor. Synthesis. We demonstrate that the evolution of prior selfing may increase population growth rates of inferior competitors and may consequently promote long-term coexistence via an evolutionary rescue. This constitutes a novel mechanism explaining the co-evolutionary coexistence of closely related plant species without niche partitioning, and is consistent with recent studies reporting that closely related species with mixed mating systems can co-occur sympatrically, even under conditions of mutual reproductive interference.

    DOI: 10.1111/1365-2745.13768

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  • Covering and shading by neighbouring plants diminish pollinator visits to and reproductive success of a forest edge specialist dwarf species

    A. Ushimaru, I. Rin, K. R. Katsuhara

    Plant Biology   23 ( 5 )   711 - 718   2021年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Wiley  

    The pollination and reproductive success of flowering plants can be negatively influenced in various ways by neighbouring heterospecific plants, such as resource competition and reproductive interference. We hypothesized that covering together with shading by neighbouring plants may reduce pollinator visits to and reproductive success of plants by reducing floral attractiveness and pollinator activity and by interrupting flower access, respectively.To test this hypothesis, we examined whether shaded and covered flowers suffered from pollinator limitation and low reproductive success in a population of the dwarf herb Lithospermum zollingeri, which co-exists with woody and herbaceous plants in anthropogenically maintained forest edge meadows. Here, shaded and covered flowers were defined as those beneath the shade of the woods and those whose front portion was covered by any vegetative part of neighbouring plants, respectively.The shaded and covered flowers were visited by significantly fewer pollinators than sunlit and open flowers in the field. However, three major pollinator species responded differently to shading and covering. Significant pollen limitation reduced seed set in covered flowers, and shaded flowers produced fewer seeds. Pollen removal from the anthers was not influenced by shading or covering.Our study demonstrates the negative effects of covering on pollinator visits and seed production. It also elucidates the negative effects of shading on reproductive success in L. zollingeri, which depends on managed semi-natural conditions. Land management abandonment, which has increased shaded and covered conditions in artificial forest edge meadows and open forest floors, might promote a rapid reduction in the populations of such dwarf plants.

    DOI: 10.1111/plb.13267

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    その他リンク: https://onlinelibrary.wiley.com/doi/full-xml/10.1111/plb.13267

  • The effects of temporal continuities of grasslands on the diversity and species composition of plants

    Taiki Inoue, Yuki A. Yaida, Yuki Uehara, Koki R. Katsuhara, Jun Kawai, Keiko Takashima, Atushi Ushimaru, Tanaka Kenta

    ECOLOGICAL RESEARCH   36 ( 1 )   24 - 31   2021年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Seminatural grasslands are ecosystems rich in biodiversity. However, their decline has been reported worldwide, and identification of grasslands with high conservation priority is urgently required. Recently, an increasing number of studies have reported that past vegetation history affects current biological communities. To evaluate whether the temporal continuity of grasslands promotes biodiversity, and thus can be an indicator of conservation priority, we studied vascular plant communities in old (160-1000s years) and new (52-70 years after deforestation) grasslands, as well as in forests, of Sugadaira Highland in central Japan. The number of plant species was highest in old grasslands, followed by new grasslands and forests. This pattern was much clearer in the number of grassland-dependent native and grassland-dependent endangered species, indicating the role of old grasslands as refugia for those species. The species composition differed between old and new grasslands. New grasslands had species compositions in between those of old grasslands and forests, suggesting that the plant community in new grasslands retains the influence of past forestation for more than 52 years after deforestation. Eleven indicator species were detected in old grasslands, but none in new grasslands, suggesting the uniqueness of the plant community in old grasslands. We conclude that the temporal continuity of grasslands increases plant diversity and can be an indicator of grasslands with high conservation priority.

    DOI: 10.1111/1440-1703.12169

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  • Prior selfing can mitigate the negative effects of mutual reproductive interference between coexisting congeners

    Koki R. Katsuhara, Atushi Ushimaru

    FUNCTIONAL ECOLOGY   33 ( 8 )   1504 - 1513   2019年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    When more than one closely related plant species share the same pollination niche, reproductive interference via interspecific pollen transfer should limit their coexistence. However, some studies have reported the sympatric coexistence of two native close relatives pollinated by the same pollinators under reproductive interference, even without niche partitioning. We examined the frequency dependency of reproductive interference between close relatives in natural conditions and the potential roles of autonomous selfing in mitigating the negative reproductive interference effects between congeneric species. We investigated sympatrically growing Commelina communis (Cc) and C. c. f. ciliata (Ccfc) populations. These species exhibit very large overlaps in habitat preference, flowering phenology and pollination niche, but seldom produce hybrids. First, we conducted a hand-pollination experiment to examine the negative effects of heterospecific pollen deposition on seed production and the potential of self-pollination to mitigate the effects in both species. Then, we examined the effects of reproductive interference on reproductive success and the potential for autonomous selfing in the field. We found significant negative effects of heterospecific pollen deposition on seed production and the mitigation effects of prior and competing self-pollination, in both Cc and Ccfc. For both species in the field, intraspecific pollinator movements and reproductive success significantly decreased with an increase in the relative floral abundance of competing species, although the negative reproductive interference effect on reproductive success was lower in Cc than in Ccfc. We also found greater potential for prior autonomous selfing in Cc than in Ccfc. Our findings suggest that Cc flowers were less affected by reproductive interference from competing species, which was likely due to a higher prior selfing ability compared to Ccfc flowers. The asymmetry in susceptibility to reproductive interference may explain the Cc-biased distribution in the study area. The study improves our understanding of how prior autonomous selfing can reduce the negative reproductive interference effect from competing species in mixed-mating species with frequent pollinator visits. A plain language summary is available for this article.

    DOI: 10.1111/1365-2435.13344

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  • Ski runs as an alternative habitat for threatened grassland plant species in Japan

    Yuki A. Yaida, Takuma Nagai, Kazuya Oguro, Koki R. Katsuhara, Kei Uchida, Tanaka Kenta, Atushi Ushimaru

    Palaearctic Grassland   42   16 - 22   2019年6月

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  • Development of microsatellite markers for the annual andromonoecious herb Commelina communis f. ciliata (Commelinaceae)

    Koki R. Katsuhara, Naoyuki Nakahama, Taketo Komura, Masaya Kato, Yuko Miyazaki, Yuji Isagi, Motomi Ito, Atushi Ushimaru

    GENES & GENETIC SYSTEMS   94 ( 3 )   133 - 138   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:GENETICS SOC JAPAN  

    Commelina communis f. ciliata (Commelinaceae), a newly distinguished taxon, is an annual andromonoecious herb exhibiting a mixed mating system, the details of which remain unclear. We developed microsatellite markers for use in exploring the evolution of andromonoecy and mixed mating in the species. Fifteen micro satellite loci were developed using next-generation sequencing. The primer sets were used to evaluate 65 C. communis f. ciliata individuals from three populations in Japan; we found 1-13 alleles per locus and the expected heterozygosity ranged from 0.00 to 0.76. The markers are potentially useful to examine intra- and inter-species genetic structure and the mixed mating strategy of Commelina species via paternity analysis.

    DOI: 10.1266/ggs.18-00058

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  • Functional significance of petals as landing sites in fungus-gnat pollinated flowers of Mitella pauciflora (Saxifragaceae)

    Koki R. Katsuhara, Shumpei Kitamura, Atushi Ushimaru

    FUNCTIONAL ECOLOGY   31 ( 6 )   1193 - 1200   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Despite the well-known visual attraction function of angiosperm petals, additional roles of these floral organs (e.g. the provision of landing-site platforms for pollinators) have rarely been examined. This is likely because most petals perform multiple functions, making it difficult to isolate the importance of landing sites in pollination success. We investigated the landing-site function of dull-coloured pinnately branched petals in Mitella pauciflora flowers, which are predominantly pollinated by fungus gnats. We conducted a field experiment, in which the effects of experimental petal removal on pollinators' approach, landing and visit duration and floral reproductive success were examined in naturally pollinated flowers. According to direct and time-lapse camera observations, petal removal did not influence pollinators' approach frequency or visit duration, but did significantly decrease their landings. Fruit set and pollen dispatch both significantly decreased with petal removal, indicating that petals promote female and male reproductive success in M.pauciflora by facilitating pollinator landing. This demonstrates that inconspicuous petals primarily have a landing-site function rather than a visual attraction function in M.pauciflora. Discriminating between diverse petal functions is a challenging problem, and new approaches are required to elucidate the functional features of angiosperm flowers.A is available for this article.

    DOI: 10.1111/1365-2435.12842

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  • Environmental DNA reflects spatial and temporal jellyfish distribution

    Toshifumi Minamoto, Miho Fukuda, Koki R. Katsuhara, Ayaka Fujiwara, Shunsuke Hidaka, Satoshi Yamamoto, Kohji Takahashi, Reiji Masuda

    PLOS ONE   12 ( 2 )   2017年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PUBLIC LIBRARY SCIENCE  

    Recent development of environmental DNA (eDNA) analysis allows us to survey underwater macro-organisms easily and cost effectively; however, there have been no reports on eDNA detection or quantification for jellyfish. Here we present the first report on an eDNA analysis of marine jellyfish using Japanese sea nettle (Chrysaora pacifica) as a model species by combining a tank experiment with spatial and temporal distribution surveys. We performed a tank experiment monitoring eDNA concentrations over a range of time intervals after the introduction of jellyfish, and quantified the eDNA concentrations by quantitative real-time PCR. The eDNA concentrations peaked twice, at 1 and 8 h after the beginning of the experiment, and became stable within 48 h. The estimated release rates of the eDNA in jellyfish were higher than the rates previously reported in fishes. A spatial survey was conducted in June 2014 in Maizuru Bay, Kyoto, in which eDNA was collected from surface water and sea floor water samples at 47 sites while jellyfish near surface water were counted on board by eye. The distribution of eDNA in the bay corresponded with the distribution of jellyfish inferred by visual observation, and the eDNA concentration in the bay was similar to 13 times higher on the sea floor than on the surface. The temporal survey was conducted from March to November 2014, in which jellyfish were counted by eye every morning while eDNA was collected from surface and sea floor water at three sampling points along a pier once a month. The temporal fluctuation pattern of the eDNA concentrations and the numbers of observed individuals were well correlated. We conclude that an eDNA approach is applicable for jellyfish species in the ocean.

    DOI: 10.1371/journal.pone.0173073

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▼全件表示

共同研究・競争的資金等の研究

  • 都市環境下における在来植物集団の遺伝的多様性と存続可能性の評価

    研究課題/領域番号:21K17914  2021年04月 - 2026年03月

    日本学術振興会  科学研究費助成事業 若手研究  若手研究

    勝原 光希

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    配分額:4290000円 ( 直接経費:3300000円 、 間接経費:990000円 )

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  • 繁殖干渉下の共存を可能にする進化的救済のメカニズム

    研究課題/領域番号:20J01271  2020年04月 - 2023年03月

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    勝原 光希

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    配分額:4810000円 ( 直接経費:3700000円 、 間接経費:1110000円 )

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  • 繁殖干渉下における在来近縁植物種の共存機構の解明‐ツユクサ・ケツユクサ系を用いて

    研究課題/領域番号:17J01902  2017年04月 - 2020年03月

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    勝原 光希

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    配分額:2800000円 ( 直接経費:2800000円 )

    植物の多種共存機構の解明は生態学における中心的議題であり、伝統的には、それらは異なる送粉者に適応した花形態や開花期のずれといった、ニッチ分割理論によって説明されてきた。本研究では、「先行自家受粉率の進化が繁殖干渉下の2種共存を可能にする」という仮説の検証を目的とし、本年度はツユクサ・ケツユクサ野外集団における集団遺伝学的な調査及び、数理モデルを用いたシミュレーションによる共存条件の模索を行った。
    まず、繁殖干渉が集団の遺伝構造や自殖率に与える影響について検証を行った。昨年度までに開発したケツユクサに適応可能なマイクロサテライトマーカーを用いて、ツユクサとケツユクサの共存集団とケツユクサの単独集団から採取した葉のDNAを抽出しジェノタイピングを行い、集団間の遺伝構造や自殖率の比較を行った。結果から、共存集団では、単独集団と比較し、遺伝的多様性は変化しない一方で、近交係数や推定自殖率が増加する傾向があることが明らかになった。このことは、繁殖干渉の存在下で自殖的な個体が増加していることを示唆している。
    さらに数理モデルを用いたシミュレーションから、、送粉者量や近交弱勢等のパラメータについて、共存を可能にするパラメータ領域について詳細な解析を行った。結果から、中程度の送粉者制限があること、及び、近交弱勢の強度が集団の自殖率の増加に伴って減少すること条件では、2種で先行自家受粉が共進化することによって長期的な共存が可能になることが示唆された。これらの結果は、繁殖干渉下での近縁種の共存機構を、従来の理論であるニッチの分割や空間構造を伴う棲み分け等とは異なる視点から説明するものであり、植物の多種共存メカニズムだけでなく、植物の多様な繁殖様式の進化に関する知見を深める重要な発見である。

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担当授業科目

  • 保全植物学 (2021年度) 後期  - 木6~7

  • 応用生態学演習 (2021年度) 前期  - その他

  • 応用生態学演習 (2021年度) 後期  - その他

  • 環境・社会基盤系入門 (2021年度) 第1学期  - 水1~2

  • 環境生物学実験 (2021年度) 第1学期  - 火5~7,金5~7