Rodrigues António M M, Gardner Andy
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK Wolfson College, Barton Road, Cambridge CB3 9BB, UK
School of Biology, University of St Andrews, Dyers Brae, St Andrews KY16 9TH, UK.
Proc Biol Sci. 2015 Jul 7;282(1810). doi: 10.1098/rspb.2015.0570.
Local mate competition (LMC) occurs when male relatives compete for mating opportunities, and this may favour the evolution of female-biased sex allocation. LMC theory is among the most well developed and empirically supported topics in behavioural ecology, clarifies links between kin selection, group selection and game theory, and provides among the best quantitative evidence for Darwinian adaptation in the natural world. Two striking invariants arise from this body of work: the number of sons produced by each female is independent of both female fecundity and also the rate of female dispersal. Both of these invariants have stimulated a great deal of theoretical and empirical research. Here, we show that both of these invariants break down when variation in female fecundity and limited female dispersal are considered in conjunction. Specifically, limited dispersal of females following mating leads to local resource competition (LRC) between female relatives for breeding opportunities, and the daughters of high-fecundity mothers experience such LRC more strongly than do those of low-fecundity mothers. Accordingly, high-fecundity mothers are favoured to invest relatively more in sons, while low-fecundity mothers are favoured to invest relatively more in daughters, and the overall sex ratio of the population sex ratio becomes more female biased as a result.
当雄性亲属为交配机会而竞争时，就会发生本地配偶竞争（LMC），这可能有利于偏向雌性的性别分配的进化。LMC理论是行为生态学中发展最为完善且得到实证支持的主题之一，它阐明了亲缘选择、群体选择和博弈论之间的联系，并为自然界中达尔文式适应提供了最佳的定量证据之一。这项研究成果产生了两个显著的不变量：每个雌性所产儿子的数量既独立于雌性的繁殖力，也独立于雌性的扩散率。这两个不变量都激发了大量的理论和实证研究。在这里，我们表明，当同时考虑雌性繁殖力的变化和有限的雌性扩散时，这两个不变量都不成立。具体而言，交配后雌性的有限扩散导致雌性亲属之间为繁殖机会而进行本地资源竞争（LRC），高繁殖力母亲的女儿比低繁殖力母亲的女儿经历的这种LRC更强烈。因此，高繁殖力母亲倾向于在儿子身上投入相对更多，而低繁殖力母亲则倾向于在女儿身上投入相对更多，结果种群的总体性别比变得更加偏向雌性。
