Data from: Sex-specific selection under environmental stress in seed beetles

Sexual selection can increase rates of adaptation by imposing stronger 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 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 stress-levels. While 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 and each 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（sexual selection）可通过对雄性施加更强的选择压力，提升种群适应速率，从而以较低的种群统计成本高效清除种群适合度上的突变负荷。诚然，整个动物界的性选择往往偏向雄性，但鲜有实证研究探讨这一性别差异的生态敏感性。本研究针对性选择的性别特异性强度、环境敏感性以及基因型-环境互作（genotype-by-environment interactions）生成了理论预测，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验证。我们利用14个等雌性品系（isofemale lines），测定了两性在幼体和成体阶段的适合度组分（fitness components）降幅、基因型-环境互作情况，以及选择强度（即适合度方差，variance in fitness）。正如理论预测所示，适合度方差随胁迫强度升高而增大，且成体繁殖成功率的适合度方差在雄性中始终大于雌性（这表明存在较强的性选择），但在所有胁迫水平下，幼体存活率的适合度方差在两性间并无显著差异。尽管严重胁迫下适合度遗传方差（genetic variance in fitness）有所升高，但遗传力（heritability）却出现下降，雄性群体的下降尤为显著。此外，适合度相关的基因型-环境互作较为普遍，但具体取决于胁迫类型、性别以及生活史阶段，这表明新环境可能会改变两性间选择的相对方向与强度。因此，本研究阐明了环境胁迫如何影响自然选择（natural selection）与性选择的相对作用力，以及适合度遗传方差的伴随变化，而这些变化预计会对有性繁殖种群的适应速率产生影响。