Division of Population and Evolutionary Biology, School of Biological Sciences, Crown Street, University of Liverpool, Liverpool, L69 7ZB, UK.
Biol Rev Camb Philos Soc. 2010 Nov;85(4):897-934. doi: 10.1111/j.1469-185X.2010.00140.x.
Sperm competition was identified in 1970 as a pervasive selective force in post-copulatory sexual selection that occurs when the ejaculates of different males compete to fertilise a given set of ova. Since then, sperm competition has been much studied both empirically and theoretically. Because sperm competition often favours large ejaculates, an important challenge has been to understand the evolution of strategies through which males invest in sperm production and economise sperm allocation to maximise reproductive success under competitive conditions. Sperm competition mechanisms vary greatly, depending on many factors including the level of sperm competition, space constraints in the sperm competition arena, male mating roles, and female influences on sperm utilisation. Consequently, theoretical models of ejaculate economics are complex and varied, often with apparently conflicting predictions. The goal of this review is to synthesise the theoretical basis of ejaculate economics under sperm competition, aiming to provide empiricists with categorised model assumptions and predictions. We show that apparent contradictions between older and newer models can often be reconciled and there is considerable consensus in the predictions generated by different models. We also discuss qualitative empirical support for some of these predictions, and detail quantitative matches between predictions and observations that exist in the yellow dung fly. We argue that ejaculate economic theory represents a powerful heuristic to explain the diversity in ejaculate traits at multiple levels: across species, across males and within individual males. Future progress requires greater understanding of sperm competition mechanisms, quantification of trade-offs between ejaculate allocation and numbers of matings gained, further knowledge of mechanisms of female sperm selection and their associated costs, further investigation of non-sperm ejaculate effects, and theoretical integration of pre- and post-copulatory episodes of sexual selection.
精子竞争在 1970 年被确定为一种普遍存在的、发生在不同雄性个体的精液竞争受精给定卵子集合的后交配性选择的选择压力。从那时起，精子竞争在经验和理论上都得到了广泛的研究。由于精子竞争通常有利于大的精液量，因此一个重要的挑战是理解雄性在精子生产上的投资策略和在竞争条件下最大化繁殖成功率的精子分配策略的进化。精子竞争机制因许多因素而异，包括精子竞争的程度、精子竞争场的空间限制、雄性交配角色以及雌性对精子利用的影响。因此，精液经济学的理论模型非常复杂和多样化，通常会有明显相互矛盾的预测。本综述的目的是综合精子竞争下的精液经济学的理论基础，旨在为经验主义者提供分类的模型假设和预测。我们表明，旧模型和新模型之间的明显矛盾通常可以调和，并且不同模型生成的预测存在相当大的共识。我们还讨论了一些预测的定性实证支持，并详细说明了在黄粪蝇中存在的预测与观察之间的定量匹配。我们认为，精液经济理论代表了一种强大的启发式方法，可以解释在多个层面上的精液特征的多样性：跨越物种、跨越雄性个体和个体内部。未来的进展需要更好地理解精子竞争机制、量化精液分配与交配次数之间的权衡、进一步了解雌性精子选择及其相关成本的机制、进一步研究非精子精液效应、以及将前交配和后交配性选择的理论进行综合。
