Department Behavioural Ecology and Evolutionary Genetics, The Max Planck Institute for Ornithology, D-82319 Seewiesen, Germany.
Proc Natl Acad Sci U S A. 2011 Jun 28;108(26):10608-13. doi: 10.1073/pnas.1103195108. Epub 2011 Jun 13.
In many species that form socially monogamous pair bonds, a considerable proportion of the offspring is sired by extrapair males. This observation has remained a puzzle for evolutionary biologists: although mating outside the pair bond can obviously increase the offspring production of males, the benefits of such behavior to females are less clear, yet females are known to actively solicit extrapair copulations. For more than two decades adaptionist explanations have dominated the discussions, yet remain controversial, and genetic constraint arguments have been dismissed without much consideration. An intriguing but still untested hypothesis states that extrapair mating behavior by females may be affected by the same genetic variants (alleles) as extrapair mating behavior by males, such that the female behavior could evolve through indirect selection on the male behavior. Here we show that in the socially monogamous zebra finch, individual differences in extrapair mating behavior have a hereditary component. Intriguingly, this genetic basis is shared between the sexes, as shown by a strong genetic correlation between male and female measurements of extrapair mating behavior. Hence, positive selection on males to sire extrapair young will lead to increased extrapair mating by females as a correlated evolutionary response. This behavior leads to a fundamentally different view of female extrapair mating: it may exist even if females obtain no net benefit from it, simply because the corresponding alleles were positively selected in the male ancestors.
在许多形成社会一夫一妻制伴侣关系的物种中，相当一部分后代是由婚外雄性所生育的。这一观察结果一直令进化生物学家感到困惑：尽管与伴侣之外的雄性交配显然可以增加雄性后代的繁殖数量，但这种行为对雌性的好处却不太清楚，尽管众所周知雌性会主动寻求婚外交配。二十多年来，适应论解释一直主导着讨论，但仍然存在争议，而遗传约束论点则没有经过太多考虑就被驳回了。一个有趣但尚未经过测试的假设表明，雌性的婚外交配行为可能受到与雄性婚外交配行为相同的遗传变异（等位基因）的影响，因此雌性行为可以通过对雄性行为的间接选择来进化。在这里，我们表明在社会一夫一妻制的斑马雀中，婚外交配行为的个体差异具有遗传成分。有趣的是，正如婚外交配行为的雄性和雌性测量值之间存在强烈的遗传相关性所表明的那样，这种遗传基础在两性之间是共享的。因此，对雄性进行直接选择以生育婚外后代将导致雌性婚外交配的增加，这是一种相关的进化反应。这种行为导致了对雌性婚外交配的根本不同看法：即使雌性从中没有获得任何净收益，它也可能存在，仅仅是因为相应的等位基因在雄性祖先中受到了积极选择。
