Department of Genetics, University of Pretoria, Pretoria, South Africa.
J Theor Biol. 2011 Dec 7;290:81-7. doi: 10.1016/j.jtbi.2011.08.030. Epub 2011 Aug 27.
Female biased sex ratios reduce competition between brothers when mating takes place within local patches. Male dispersal prior to mating is another strategy that reduces competition between brothers. One may thus expect these two traits to co-evolve and this is partially met in that sex ratios becomes less female biased as dispersal increases. However, the evolutionary stable degree of dispersal is unaffected by the sex ratio. The analytical models developed to reach these conclusions ignored variance in sex ratios, since this increases the structural complexity of models. For similar reasons finite clutch sizes are also routinely ignored. To overcome these shortfalls, we developed individual based simulations that allowed us to incorporate realistic clutch sizes and binomial variance in sex ratios between patches. We show that under variable sex ratios, males evolve to more readily disperse away from patches with higher sex ratios than lower sex ratios. We show that, while the dispersal rate is insensitive to the sex ratio when sex ratios are precise, it is affected by the number of males with dispersal decreasing as the number of males decreases.
当交配发生在局部斑块内时，雌性偏性性别比例会降低兄弟之间的竞争。交配前的雄性扩散是另一种降低兄弟间竞争的策略。因此，人们可能期望这两个特征共同进化，这在一定程度上得到了满足，即随着扩散的增加，性别比例的雌性偏性程度降低。然而，性比率对扩散的稳定进化程度没有影响。为了得出这些结论，所开发的分析模型忽略了性别比例的方差，因为这增加了模型的结构复杂性。出于类似的原因，通常也忽略了有限的卵群大小。为了克服这些缺陷，我们开发了基于个体的模拟，使我们能够将现实的卵群大小和斑块之间性别比例的二项式方差纳入其中。我们表明，在可变性别比例下，雄性进化为更容易从性别比例较高的斑块扩散出去，而不是从性别比例较低的斑块扩散出去。我们表明，虽然当性别比例精确时，扩散率对性别比例不敏感，但当雄性数量减少时，扩散率会受到影响，因为雄性的数量减少。
