Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
Philos Trans R Soc Lond B Biol Sci. 2020 Dec 7;375(1813):20200082. doi: 10.1098/rstb.2020.0082. Epub 2020 Oct 19.
Although initially lagging behind discoveries being made in other taxa, mammalian sperm competition is now a productive and advancing field of research. Sperm competition in mammals is not merely a 'sprint-race' between the gametes of rival males, but rather a race over hurdles; those hurdles being the anatomical and physiological barriers provided by the female reproductive tract, as well as the egg and its vestments. With this in mind, in this review, I discuss progress in the field while focusing on the female perspective. I highlight ways by which sperm competition can have positive effects on female reproductive success and discuss how competitive outcomes are not only owing to dynamics between the ejaculates of rival males, but also attributable to mechanisms by which female mammals bias paternity toward favourable sires. Drawing on examples across different species-from mice to humans-I provide an overview of the accumulated evidence which firmly establishes that sperm competition is a key selective force in the evolution of male traits and detail how females can respond to increased sperm competitiveness with increased egg resistance to fertilization. I also discuss evidence for facultative responses to the sperm competition environment observed within mammal species. Overall, this review identifies shortcomings in our understanding of the specific mechanisms by which female mammals 'select' sperm. More generally, this review demonstrates how, moving forward, mammals will continue to be effective animal models for studying both evolutionary and facultative responses to sperm competition. This article is part of the theme issue 'Fifty years of sperm competition'.
尽管最初在其他分类群的发现中落后，但哺乳动物的精子竞争现在是一个富有成效和不断发展的研究领域。哺乳动物的精子竞争不仅仅是竞争雄性配子之间的“短跑比赛”，而是一场跨越障碍的比赛；这些障碍是雌性生殖道、卵子及其附属物提供的解剖学和生理学屏障。考虑到这一点，在本次综述中，我讨论了该领域的进展，同时重点关注女性视角。我强调了精子竞争如何对女性生殖成功产生积极影响，并讨论了竞争结果不仅归因于竞争雄性的精液之间的动态，还归因于雌性哺乳动物偏向有利父本的机制。通过引用从老鼠到人类等不同物种的例子，我概述了积累的证据，这些证据确凿地证明了精子竞争是雄性特征进化的关键选择力量，并详细说明了雌性哺乳动物如何通过增加卵子对受精的抵抗力来应对精子竞争力的提高。我还讨论了在哺乳动物物种中观察到的对精子竞争环境的兼性反应的证据。总的来说，本综述确定了我们对雌性哺乳动物“选择”精子的具体机制的理解存在缺陷。更普遍地说，本综述表明，未来哺乳动物将继续成为研究对精子竞争的进化和兼性反应的有效动物模型。本文是主题为“精子竞争 50 年”的特刊的一部分。
