Centre for Evolutionary Biology, University of Western Australia, Western Australia, Australia.
Ann N Y Acad Sci. 2018 Jun;1422(1):48-64. doi: 10.1111/nyas.13635. Epub 2018 Mar 10.
Males and females rarely have identical evolutionary interests over reproduction, and when the fitness of both sexes is dependent upon paternity outcomes, sexual conflict over fertilization is inevitable. In internal fertilizers, the female tract is a formidable selective force on the number and integrity of sperm that reach the egg. Selection on sperm quality is intensified when females mate multiply and rival males are forced to compete for fertilizations. While male adaptations to sperm competition have been well documented (e.g., increased sperm fertilizing capacity), much less attention has been given to the evolutionary consequences of postmating sexual conflict for egg form and function. Specifically, increased sperm competitiveness can be detrimental by giving rise to an elevation in reproductive failure resulting from polyspermy. Spanning literature on both internal and external fertilizers, in this review I discuss how females respond to sperm competition via fertilization barriers that mediate sperm entry. These findings, which align directly with sexual conflict theory, indicate that females have greater control over fertilization than has previously been appreciated. I then consider the implications of gametic sexual conflict in relation to the development of reproductive isolation and speculate on potential mechanisms accounting for "egg defensiveness." Finally, I discuss the functional significance of egg defensiveness for both the sexes, and sperm selection for females.
男性和女性在生殖方面很少有完全相同的进化利益，当两性的适应度都依赖于亲代结果时，受精过程中的性冲突是不可避免的。在体内受精的物种中，雌性生殖道对精子的数量和完整性具有强大的选择压力，这些精子才能到达卵子。当雌性多次交配并且雄性必须竞争受精时，对精子质量的选择就会加剧。虽然男性对精子竞争的适应已经得到了很好的记录（例如，增加了精子的受精能力），但对于交配后性冲突对卵子形态和功能的进化后果，关注的就少得多了。具体来说，由于多精入卵导致生殖失败的增加，增加精子竞争力可能会产生不利影响。在这篇综述中，我跨越了内部和外部受精的文献，讨论了雌性如何通过介导精子进入的受精障碍来应对精子竞争。这些发现与性冲突理论直接一致，表明雌性对受精的控制比以前认为的要大。然后，我考虑配子性冲突与生殖隔离发展的关系，并推测解释“卵子防御”的潜在机制。最后，我讨论了卵子防御对两性以及雌性的精子选择的功能意义。
