Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
Proc Natl Acad Sci U S A. 2011 Apr 26;108(17):7091-5. doi: 10.1073/pnas.1103329108. Epub 2011 Apr 11.
We summarize the literature on rates of multiple paternity and sire numbers per clutch in viviparous fishes vs. mammals, two vertebrate groups in which pregnancy is common but entails very different numbers of embryos (for species surveyed, piscine broods averaged >10-fold larger than mammalian litters). As deduced from genetic parentage analyses, multiple mating by the pregnant sex proved to be common in assayed species but averaged significantly higher in fish than mammals. However, within either of these groups we found no significant correlations between brood size and genetically deduced incidence of multiple mating by females. Overall, these findings offer little support for the hypothesis that clutch size in pregnant species predicts the outcome of selection for multiple mating by brooders. Instead, whatever factors promote multiple mating by members of the gestating sex seem to do so in surprisingly similar ways in live-bearing vertebrates otherwise as different as fish and mammals. Similar conclusions emerged when we extended the survey to viviparous amphibians and reptiles. One notion consistent with these empirical observations is that although several fitness benefits probably accrue from multiple mating, logistical constraints on mate-encounter rates routinely truncate multiple mating far below levels that otherwise could be accommodated, especially in species with larger broods. We develop this concept into a "logistical constraint hypothesis" that may help to explain these mating outcomes in viviparous vertebrates. Under the logistical constraint hypothesis, propensities for multiple mating in each species register a balance between near-universal fitness benefits from multiple mating and species-idiosyncratic logistical limits on polygamy.
我们总结了关于胎生鱼类和哺乳动物的多父本率和每窝亲代数量的文献，这两个脊椎动物群体都普遍存在妊娠现象，但胚胎数量却有很大差异（在所调查的物种中，鱼类的胚胎数量平均比哺乳动物的幼仔大 10 倍以上）。从遗传亲子关系分析推断，妊娠雌性的多次交配被证明在被检测的物种中很常见，但在鱼类中比在哺乳动物中更为普遍。然而，在这两个群体中，我们都没有发现窝卵数大小与雌性遗传推断的多次交配发生率之间存在显著相关性。总的来说，这些发现几乎没有支持这样一种假设，即妊娠物种的窝卵数大小预测了选择对亲代进行多次交配的结果。相反，促进妊娠物种中多次交配的因素似乎以相似的方式在鱼类和哺乳动物等截然不同的胎生脊椎动物中发挥作用。当我们将调查扩展到胎生两栖动物和爬行动物时，也得出了类似的结论。与这些经验观察一致的一个观点是，尽管多次交配可能带来几种适应度益处，但对配偶相遇率的逻辑限制通常会将多次交配大大缩短到否则可以容纳的水平以下，尤其是在窝卵数较大的物种中。我们将这个概念发展成一个“逻辑限制假说”，该假说可以帮助解释胎生脊椎动物中的这些交配结果。根据逻辑限制假说，每个物种的多次交配倾向反映了从多次交配中获得的近乎普遍的适应度益处与物种特有的多配偶制逻辑限制之间的平衡。
