Sawada Kota, Yamaguchi Sachi, Iwasa Yoh
Department of Evolutionary Studies of Biosystems, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan.
Department of Information Systems Creation, Faculty of Engineering, Kanagawa University, Yokohama, Kanagawa 221-8686, Japan.
J Theor Biol. 2017 May 21;421:127-135. doi: 10.1016/j.jtbi.2017.03.029. Epub 2017 Apr 1.
Among animals living in groups with reproductive skew associated with a dominance hierarchy, subordinates may do best by using various alternative tactics. Sequential hermaphrodites or sex changers adopt a unique solution, that is, being the sex with weaker skew when they are small and subordinate, and changing sex when they become larger. In bi-directionally sex-changing fishes, although most are haremic and basically protogynous, subordinate males can change sex to being females. We study a mathematical model to examine when and why such reversed sex change is more adaptive than dispersal to take over another harem. We attempt to examine previously proposed hypotheses that the risk of dispersal and low density favor reversed sex change, and to specify an optimal decision-making strategy for subordinates. As a result, while the size-dependent conditional strategy in which smaller males tend to change sex is predicted, even large males are predicted to change sex under low density and/or high risk of dispersal, supporting both previous hypotheses. The importance of spatiotemporal variation of social and ecological conditions is also suggested. We discuss a unified framework to understand hermaphroditic and gonochoristic societies.
在具有与优势等级制度相关的生殖偏斜的群居动物中，从属个体可能通过采用各种替代策略来达到最佳状态。顺序雌雄同体或性转变者采用了一种独特的解决方案，即当它们体型较小且处于从属地位时成为偏斜较弱的性别，并在体型变大时转变性别。在双向性转变鱼类中，尽管大多数是一雄多雌制且基本上是雌性先熟，但从属雄性可以转变为雌性。我们研究了一个数学模型，以研究这种反向性转变在何时以及为何比分散到另一个一雄多雌群体中更具适应性。我们试图检验先前提出的假设，即分散的风险和低密度有利于反向性转变，并为从属个体确定一种最优决策策略。结果，虽然预测了较小雄性倾向于转变性别的大小依赖条件策略，但预计即使是大型雄性在低密度和/或高分散风险下也会转变性别，这支持了先前的两个假设。还提出了社会和生态条件时空变化的重要性。我们讨论了一个统一的框架来理解雌雄同体和雌雄异体的社会。
