Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom.
Am Nat. 2013 Oct;182(4):421-38. doi: 10.1086/671994. Epub 2013 Aug 23.
Hamilton's haplodiploidy hypothesis suggests that the relatively higher relatedness of full sisters in haplodiploid populations promotes altruistic sib rearing and, consequently, the evolution of eusociality. This haplodiploidy effect works when some broods have a relatively female-biased sex ratio and other broods have a relatively male-biased sex ratio, termed split sex ratios. There is empirical evidence for two scenarios having potentially led to split sex ratios en route to eusociality: unmated queens and queen replacement. A recent analysis of these two scenarios has suggested that haplodiploidy can either promote or inhibit the evolution of eusociality and that the effect is usually small. However, this work made the simplifying assumptions that there is only negligible reproduction by workers and that their offspring have the same sex ratio as those produced by the queen. Here, we relax these assumptions and find that worker reproduction has a negative influence on the evolution of helping, either reducing the extent to which it is promoted or leading to it being inhibited. This is particularly so when workers are unmated and hence constrained to produce only sons, by arrhenotoky. Overall, when parameterized with empirical data, our results suggest that split sex ratios in haplodiploid species have not played an important role in facilitating the evolution of eusociality.
汉密尔顿的单倍二倍体假说表明，在单倍二倍体种群中，全同胞之间相对较高的亲缘关系促进了利他的同胞养育，从而促进了真社会性的进化。当一些巢具有相对雌性偏性的性别比，而其他巢具有相对雄性偏性的性别比时，这种单倍二倍体效应就会起作用，这种性别比称为分裂性别比。有实证证据表明，有两种情况可能导致真社会性进化过程中出现分裂性别比：未交配的蜂王和蜂王更替。最近对这两种情况的分析表明，单倍二倍体既可以促进也可以抑制真社会性的进化，而且这种影响通常很小。然而，这项工作做出了一些简化假设，即工蜂的繁殖几乎可以忽略不计，而且它们的后代与蜂王所产的后代具有相同的性别比。在这里，我们放松了这些假设，并发现工蜂的繁殖对帮助的进化有负面影响，要么减少它被促进的程度，要么导致它被抑制。当工蜂未交配且因此只能通过孤雌生殖产生雄性时，这种情况尤其如此。总的来说，当用实证数据参数化时，我们的结果表明，单倍二倍体物种中的分裂性别比并没有在促进真社会性的进化中发挥重要作用。
