Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, 35 Stirling Hwy, Crawley, Western Australia 6009, Australia.
Proc Biol Sci. 2020 May 13;287(1926):20192909. doi: 10.1098/rspb.2019.2909. Epub 2020 May 6.
A shift from the traditional perspective that maternal stress is invariably costly has instigated recent interest into its adaptive role in offspring sex allocation. Stress generated by social instability has been linked to offspring sex ratio biases that favour the production of female offspring, which converges with the theoretical prediction that mothers in the poor condition are better off investing in daughters rather than sons. However, previous research has failed to disentangle two different processes: the passive consequence of maternal stress on sex-specific mortality and the adaptive effect of maternal stress at the time of conception. Here, I show that exposure to high male density social conditions leads to elevated stress hormone levels and female-biased offspring sex ratios in house mice (), and identify that sex-specific offspring production-not sex-specific mortality-is the mechanism accounting for these sex ratio skews. This outcome reflects the optimal fitness scenario for mothers in a male-dominated environment: the production of daughters, who are guaranteed high mate availability, minimizes male-male competition for their sons. Overall, this study supports the idea that maternal stress has the potential to be adaptive and advances our understanding of how exposure to different social conditions can influence sex allocation in mammals.
从传统观点来看，母体压力总是有代价的，但这种观点已经发生了转变，最近人们开始关注母体压力在后代性别分配中的适应作用。社会不稳定产生的压力与有利于产生雌性后代的后代性别比例偏差有关，这与理论预测一致，即处于贫困环境中的母亲通过投资于女儿而不是儿子来获得更好的收益。然而，先前的研究未能区分两种不同的过程：母体压力对性别特异性死亡率的被动影响和母体压力在受孕时的适应效应。在这里，我表明，暴露于高雄性密度的社会条件会导致家鼠（）的应激激素水平升高和雌性偏向的后代性别比例，并确定产生特定性别的后代而不是特定性别的死亡率是导致这些性别比例偏差的机制。这一结果反映了在雄性主导的环境中母亲的最佳适应情景：生产女儿，她们保证了高的交配机会，最大限度地减少了儿子之间的雄性竞争。总的来说，这项研究支持了母体压力具有适应性的观点，并增进了我们对不同社会条件如何影响哺乳动物性别分配的理解。
