Division of Mathematical Sciences, Tokyo Woman's Christian University, Tokyo, Japan.
Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Hyogo, Japan.
J Theor Biol. 2021 Mar 21;513:110594. doi: 10.1016/j.jtbi.2021.110594. Epub 2021 Jan 16.
Androdioecy, the coexistence of hermaphrodites and males, is very rare in vertebrates but occurs in mangrove killifish living in ephemeral or unstable habitats. Hermaphrodites reproduce both by outcrossing with males and by selfing. Outbreeding is advantageous because of inbreeding depression, but it requires encounters with males. The advantages of a propensity for outcrossing among hermaphrodites and the production of males affect each other very strongly. To study the evolutionary coupling of these two aspects, we here analyze a simple evolutionary game for a population composed of three phenotypes: outcrossing-oriented hermaphrodites, selfing-oriented hermaphrodites, and males. Outcrossing-oriented hermaphrodites first attempt to search for males and perform outcrossing if they encounter males. If they fail to encounter males, they reproduce via selfing. Selfing-oriented hermaphrodites simply reproduce by selfing. The replicator dynamics may show bistability, in which both the androdioecious population (with outcrossing-oriented hermaphrodites and males) and the pure hermaphroditic population are locally stable. The model shows the fraction of males is either zero or relatively high (more than 25%), which is not consistent with the observed low fraction of males (less than 5%). To explain this discrepancy, we studied several models including immigration and enforced copulation. We concluded that the observed pattern can be most likely explained by a population dominated by selfing-oriented hermaphrodites receiving immigration of males.
雌雄同体和雄性共存的雌雄同体，在脊椎动物中非常罕见，但在生活在短暂或不稳定栖息地的红树林食蚊鱼中存在。雌雄同体通过与雄性杂交和自交进行繁殖。由于近亲繁殖衰退，杂交繁殖是有利的，但它需要与雄性相遇。雌雄同体倾向于杂交和产生雄性的优势彼此强烈影响。为了研究这两个方面的进化耦合，我们在这里分析了一个由三种表型组成的简单进化博弈：倾向于杂交的雌雄同体、倾向于自交的雌雄同体和雄性。倾向于杂交的雌雄同体首先尝试寻找雄性，如果遇到雄性，则进行杂交繁殖。如果它们未能遇到雄性，则通过自交进行繁殖。倾向于自交的雌雄同体则简单地通过自交进行繁殖。复制者动态可能表现出双稳定性，其中雌雄同体种群（具有杂交倾向的雌雄同体和雄性）和纯雌雄同体种群都是局部稳定的。该模型显示雄性的比例要么为零，要么相对较高（超过 25%），这与观察到的雄性比例较低（低于 5%）不一致。为了解释这种差异，我们研究了几种模型，包括移民和强制交配。我们得出的结论是，最有可能的是，一个由自交倾向的雌雄同体为主的种群，通过雄性的移民，来解释观察到的模式。
