Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK.
J Evol Biol. 2011 Apr;24(4):904-13. doi: 10.1111/j.1420-9101.2011.02228.x. Epub 2011 Feb 10.
In cooperatively breeding species, the fitness consequences of producing sons or daughters depend upon the fitness impacts of positive (repayment hypothesis) and negative (local competition hypothesis) social interactions among relatives. In this study, we examine brood sex allocation in relation to the predictions of both the repayment and the local competition hypotheses in the cooperatively breeding long-tailed tit Aegithalos caudatus. At the population level, we found that annual brood sex ratio was negatively related to the number of male survivors across years, as predicted by the local competition hypothesis. At an individual level, in contrast to predictions of the repayment hypothesis, there was no evidence for facultative control of brood sex ratio. However, immigrant females produced a greater proportion of sons than resident females, a result consistent with both hypotheses. We conclude that female long-tailed tits make adaptive decisions about brood sex allocation.
在合作繁殖的物种中，产生儿子或女儿的适应度后果取决于亲属之间积极（回报假说）和消极（本地竞争假说）社会相互作用的适应度影响。在这项研究中，我们研究了与回报假说和本地竞争假说的预测有关的合作繁殖长尾山雀 Aegithalos caudatus 的育雏性别分配。在群体水平上，我们发现，年度育雏性别比例与多年来雄性幸存者的数量呈负相关，这与本地竞争假说的预测一致。在个体水平上，与回报假说的预测相反，没有证据表明育雏性别比例的适应性控制。然而，移民雌性比本地雌性产生更多的雄性后代，这一结果与两个假说都一致。我们的结论是，长尾山雀的雌性会对育雏性别分配做出适应性的决策。
