Martinossi-Allibert I, Arnqvist G, Berger D
Department of Ecology and Genetics, Animal Ecology, Uppsala University, Uppsala, Sweden.
J Evol Biol. 2017 Jan;30(1):161-173. doi: 10.1111/jeb.12996. Epub 2016 Nov 11.
Sexual selection can increase rates of adaptation by imposing strong selection in males, thereby allowing efficient purging of the mutation load on population fitness at a low demographic cost. Indeed, sexual selection tends to be male-biased throughout the animal kingdom, but little empirical work has explored the ecological sensitivity of this sex difference. In this study, we generated theoretical predictions of sex-specific strengths of selection, environmental sensitivities and genotype-by-environment interactions and tested them in seed beetles by manipulating either larval host plant or rearing temperature. Using fourteen isofemale lines, we measured sex-specific reductions in fitness components, genotype-by-environment interactions and the strength of selection (variance in fitness) in the juvenile and adult stage. As predicted, variance in fitness increased with stress, was consistently greater in males than females for adult reproductive success (implying strong sexual selection), but was similar in the sexes in terms of juvenile survival across all levels of stress. Although genetic variance in fitness increased in magnitude under severe stress, heritability decreased and particularly so in males. Moreover, genotype-by-environment interactions for fitness were common but specific to the type of stress, sex and life stage, suggesting that new environments may change the relative alignment and strength of selection in males and females. Our study thus exemplifies how environmental stress can influence the relative forces of natural and sexual selection, as well as concomitant changes in genetic variance in fitness, which are predicted to have consequences for rates of adaptation in sexual populations.
性选择可以通过对雄性施加强烈选择来提高适应率，从而以较低的种群统计学成本有效地清除种群适应性上的突变负荷。事实上，在整个动物界，性选择往往偏向雄性，但很少有实证研究探讨这种性别差异对生态环境的敏感性。在本研究中，我们对性别特异性的选择强度、环境敏感性以及基因型与环境的相互作用进行了理论预测，并通过操纵幼虫宿主植物或饲养温度在种子甲虫中对这些预测进行了检验。我们使用了14个单雌系，测量了幼年和成年阶段适应性成分的性别特异性降低、基因型与环境的相互作用以及选择强度（适应性方差）。正如预测的那样，适应性方差随着压力增加，在成年繁殖成功率方面，雄性的适应性方差始终大于雌性（这意味着强烈的性选择），但在所有压力水平下，幼年存活率在两性中相似。尽管在严重压力下，适应性的遗传方差在大小上有所增加，但遗传力下降，在雄性中尤其如此。此外，适应性的基因型与环境相互作用很常见，但特定于压力类型、性别和生活阶段，这表明新环境可能会改变雄性和雌性中选择的相对排列和强度。因此，我们的研究例证了环境压力如何影响自然选择和性选择的相对力量，以及适应性遗传方差的相应变化，预计这些变化会对有性种群的适应率产生影响。
