領域 名 環境生態機能学
教員氏名 安井 行雄
研究分野 進化生態学
研究キーワード：進化，適応，性選択，配偶行動
最近の研究課題
１．生物の適応進化を解明する
生物はそれぞれの生息環境に適応した性質を持っている。生物の個体群には遺伝的な変異があり 、 生息環境に適した形質をコードする遺伝子は世代を経るごとに集団中に増えていく 。 これがチャールズ ・ ダーウィンによって提唱された自然選択である 。 安井研究室では昆虫をはじめとする小型の節足動物を材料として 、 生物の適応戦略を解き明かすことを目指している 。 昆虫の色や形は彼らの生存繁殖の上でどのような機能を持つのかその美しさの秘密を探るとともに 、 世界の昆虫の多様性や里山の環境問題にも関心を持っている 。
２．雌の多回交尾の進化に関する研究
大きくて栄養豊富 な卵に比べて精子は小さくほとんど栄養を含まないので大量に生産することができる 。 そのため雄は精子数に余裕があり 、 多くの雌と交尾すればするほど子供の数 適応度 を増やすことができるが 、 雌は多数の雄と交尾しても子供の父親が入れ替わるだけで子供の数自体を増やすことはできない 。 このことから雄は無差別に多くの雌と交尾するように 、 一方雌は少数の雄を選んで大事に子供を育てるように進化していると考えられる 。 しかし多くの動物ではこの予測に反して 、 雌は複数の雄と交尾多回交尾 をしている 。 雌の多回交尾の進化は単に動物の適応戦略にとどまらず 、 人間性の起源にもせまる大きな謎として世界の研究者を魅了してきた
安井研究室ではフタホシコオロギなどの昆虫を用いてこの問題を研究している。雌が多回交尾したときにどの雄が受精するかを視覚的に判定できる白眼突然変異系統(黒目に対して劣性遺伝)を利用して、雌が多回交尾を通じて優秀な遺伝子を持つ雄や自分の遺伝子と和合性の高い雄を選んでいる、または危険分散（両賭け）をしているという仮説を検証中である。
代表的な研究業績
Yasui, Y. 1997. A “good-sperm” model can explain the evolution of costly multiple mating by females. The American
Naturalist 149: 573-584. http://www.jstor.org/stable/2463384?seq=1#page_scan_tab_contents
Yasui, Y. 1998. The ‘genetic benefits’ of female multiple mating reconsidered. Trends in Ecology and Evolution 13:
246-250. http://www.sciencedirect.com/science/article/pii/S0169534798013834
Yasui, Y. 2001. Female multiple mating as a genetic bet-hedging strategy when mate choice criteria are unreliable.
Ecological Research 16: 605-616. http://onlinelibrary.wiley.com/doi/10.1046/j.1440-1703.2001.00423.x/full
Garcia-Gonzalez, F., Yasui, Y. and Evans, J. P. 2015. Mating portfolios: bet-hedging, sexual selection and female
multiple mating. Proceedings of the Royal Society of London. Series B. Biological Sciences. vol.282
http://dx.doi.org/10.1098/rspb.2014.1525
Yasui, Y. and Garcia-Gonzalez, F. 2016. Bet-hedging as a mechanism for the evolution of polyandry, revisited.
Evolution 70: 385-397. http://onlinelibrary.wiley.com/doi/10.1111/evo.12847/abstract
Yasui, Y. and Yoshimura, J. 2018. Bet-hedging against male-caused reproductive failures may explain ubiquitous cuckoldry
in female birds. Journal of Theoretical Biology, 437: 214-221, https://doi.org/10.1016/j.jtbi.2017.10.029.
Yasui, Y. and Yamamoto, Y. 2021. An empirical test of bet-hedging polyandry hypothesis in the field cricket Gryllus
bimaculatus. Journal of Ethology 39: 329-342. https://doi.org/10.1007/s10164-021-00707-0
同誌のEditor’s Choice 2021に選定され紹介動画が作られました。
Yasui, Y. 2022. Life-history traits of the fairy shrimp Branchinella kugenumaensis are highly variable between
neighboring rice paddies in Japan. Ecological Research. 37: 344-354. https://doi.org/10.1111/1440-1703.12296
Yasui, Y. 2022. Evolutionary bet-hedging reconsidered: What is the mean–variance trade-off of fitness?
Ecological Research, 37: 406-420.https://doi.org/10.1111/1440-1703.12303
Yasui, Y. and Hasegawa, E. 2022. The origination events of gametic sexual reproduction and anisogamy.
Journal of Ethology. 40: 273-284. https://doi.org/10.1007/s10164-022-00760-3
同誌のEditor’s Choice Award 2022（論文賞）を受賞（紹介動画も作られる予定）。
Springer-Nature 2022 Research Highlights – Evolutionary Biologyに選定。https://www.ag.kagawa-u.ac.jp/?p=31001
Research Area: Environmental Science
Research Specialization: Evolutionary Ecology
Name: YASUI, Yukio
Keywords: evolution, adaptation, sexual selection, mating behavior
Recent Researches
1. Adaptive significance of insect characters
Organisms have evolved many adaptive characters to fit their environments. Genetic variation exists in any characters in species population and the genes coding adaptive characters will increase in frequency in the population through generations. This is natural selection, the evolutionary process advanced by Charles Darwin (1859). In Yasui Laboratory, we study adaptive strategies of insects and other arthropods. In particular, we are exploring adaptive significance and evolutionary function of insect coloration. Why are butterflies so beautiful? – It cannot be easily explained unlike bird ornaments because female butterflies do not choose mates based on male ornaments. We are also interested in the conservation of world insect faunas and biodiversity of Japanese “Satoyama” environments.
2. The evolution of female multiple mating or polyandry
In general, male fitness is mainly limited by the number of mates, whereas female fitness is fundamentally limited by the number of ova. Thus, sexual selection theory predicts that males tend to mate promiscuously and females should choose only one mate and invest in a limited number of offspring. However, the females of many animal species mate with more than one male in a reproductive season (polyandry). The evolution of polyandry is one of the largest
enigmas not only in animal behavior but also in regard to the origin of human nature.
We are testing several hypotheses to explain polyandry such as “good sperm” process, genetic incompatibility or bet-hedging (risk-spreading) using crickets (white eye and black eye strains).
Publications
Yasui, Y. 1997. A “good-sperm” model can explain the evolution of costly multiple mating by females. The American
Naturalist 149: 573-584. http://www.jstor.org/stable/2463384?seq=1#page_scan_tab_contents
Yasui, Y. 1998. The ‘genetic benefits’ of female multiple mating reconsidered. Trends in Ecology and Evolution 13:
246-250. http://www.sciencedirect.com/science/article/pii/S0169534798013834
Yasui, Y. 2001. Female multiple mating as a genetic bet-hedging strategy when mate choice criteria are unreliable.
Ecological Research 16: 605-616. http://onlinelibrary.wiley.com/doi/10.1046/j.1440-1703.2001.00423.x/full
Garcia-Gonzalez, F., Yasui, Y. and Evans, J. P. 2015. Mating portfolios: bet-hedging, sexual selection and female
multiple mating. Proceedings of the Royal Society of London. Series B. Biological Sciences. vol.282
http://dx.doi.org/10.1098/rspb.2014.1525
Yasui, Y. and Garcia-Gonzalez, F. 2016. Bet-hedging as a mechanism for the evolution of polyandry, revisited.
Evolution 70: 385-397. http://onlinelibrary.wiley.com/doi/10.1111/evo.12847/abstract
Yasui, Y. and Yoshimura, J. 2018. Bet-hedging against male-caused reproductive failures may explain ubiquitous cuckoldry
in female birds. Journal of Theoretical Biology, 437: 214-221, https://doi.org/10.1016/j.jtbi.2017.10.029.
Yasui, Y. and Yamamoto, Y. 2021. An empirical test of bet-hedging polyandry hypothesis in the field cricket Gryllus
bimaculatus. Journal of Ethology 39: 329-342. https://doi.org/10.1007/s10164-021-00707-0
同誌のEditor’s Choice 2021に選定され紹介動画が作られました。
Yasui, Y. 2022. Life-history traits of the fairy shrimp Branchinella kugenumaensis are highly variable between
neighboring rice paddies in Japan. Ecological Research. 37: 344-354. https://doi.org/10.1111/1440-1703.12296
Yasui, Y. 2022. Evolutionary bet-hedging reconsidered: What is the mean–variance trade-off of fitness?
Ecological Research, 37: 406-420.https://doi.org/10.1111/1440-1703.12303
Yasui, Y. and Hasegawa, E. 2022. The origination events of gametic sexual reproduction and anisogamy.
Journal of Ethology. 40: 273-284. https://doi.org/10.1007/s10164-022-00760-3
同誌のEditor’s Choice Award 2022（論文賞）を受賞（紹介動画も作られる予定）。
Springer-Nature 2022 Research Highlights – Evolutionary Biologyに選定。https://www.ag.kagawa-u.ac.jp/?p=31001
