Division of Ecology, Evolution and Genetics, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
Evolution. 2013 Oct;67(10):2838-48. doi: 10.1111/evo.12163. Epub 2013 Jun 12.
Paternity protection and the acquisition of multiple mates select for different traits. The consensus from theoretical work is that mate-guarding intensifies with an increasing male bias in the adult sex ratio (ASR). A male bias can thus lead to male monogamy if guarding takes up the entire male time budget. Given that either female- or male-biased ASRs are possible, why is promiscuity clearly much more common than male monogamy? We address this question with two models, differing in whether males can assess temporal cues of female fertility. Our results confirm the importance of the ASR: guarding durations increase with decreasing female availability and increasing number of male competitors. However, several factors prevent the mating system from switching to male monogamy as soon as the ASR becomes male biased. Inefficient guarding, incomplete last male sperm precedence, any mechanism that allows sperm to fertilize eggs after the male's departure, and (in some cases) the unfeasibility of precopulatory guarding all help explain cases where promiscuity exists on its own or alongside temporally limited mate-guarding. Shortening the window of fertilization shifts guarding time budgets from the postcopulatory to the precopulatory stage.
父权保护和获得多个配偶会选择不同的特征。理论工作的共识是，随着成年性别比例（ASR）中男性偏向的增加，配偶保护会加剧。如果保护占据了男性全部的时间预算，那么男性偏向就会导致男性一夫一妻制。鉴于雌性或雄性偏向的 ASR 都是可能的，为什么滥交显然比雄性一夫一妻制更为常见？我们通过两个模型来解决这个问题，这两个模型的区别在于雄性是否能够评估雌性生育能力的时间线索。我们的结果证实了 ASR 的重要性：随着雌性可获得性的降低和雄性竞争者数量的增加，保护时间延长。然而，有几个因素会阻止交配系统一旦 ASR 变得偏向雄性就转变为雄性一夫一妻制。保护效率低下、不完全的最后一个雄性精子优先、任何允许雄性离开后精子受精的机制，以及（在某些情况下）前置保护不可行，这些都有助于解释为什么滥交会单独存在或与有限的时间内的配偶保护同时存在。缩短受精窗口会将保护时间预算从交配后阶段转移到交配前阶段。
