Sexual selection on males is predicted to increase population fitness, and delay population extinction, when mating success negatively covaries with genetic load across individuals. However, such benefits of sexual selection could be counteracted by simultaneous increases in genome-wide drift resulting from reduced effective population size caused by increased variance in fitness. Resulting fixation of deleterious mutations could be greatest in small populations, and when environmental variation in mating traits partially decouples sexual selection from underlying genetic variation. The net consequences of sexual selection for genetic load and population persistence are therefore likely to be context dependent, but such variation has not been examined. We use a genetically explicit individual-based model to show that weak sexual selection can increase population persistence time compared to random mating. However, for stronger sexual selection such positive effects can be overturned by the detrimental effects of increased genome-wide drift. Furthermore, the relative strengths of mutation-purging and drift critically depend on the environmental variance in the male mating trait. Specifically, increasing environmental variance caused stronger sexual selection to elevate deleterious mutation fixation rate and mean selection coefficient, driving rapid accumulation of drift load and decreasing population persistence times. These results highlight an intricate balance between conflicting positive and negative consequences of sexual selection on genetic load, even in the absence of sexually antagonistic selection. They imply that environmental variances in key mating traits, and intrinsic genetic drift, should be properly factored into future theoretical and empirical studies of the evolution of population fitness under sexual selection.

中文翻译：

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雄性交配成功的环境差异调节性选择对遗传负荷的积极和消极影响。

当交配成功与个体之间的遗传负荷呈负向协变时，预计雄性的性选择会增加种群适应性，并延迟种群灭绝。然而，性选择的这种好处可能会被基因组范围漂移的同时增加所抵消，而基因组漂移的增加是由于适应性差异增加导致有效种群规模减少而导致的。当交配性状的环境变化部分地将性选择与潜在的遗传变异脱钩时，在小群体中，有害突变的固定可能是最大的。因此，性选择对遗传负荷和种群持久性的净后果可能取决于环境，但这种变异尚未得到检验。我们使用基于遗传的显性个体模型来证明，与随机交配相比，弱性选择可以增加种群持续时间。然而，对于更强的性选择，这种积极影响可能会被全基因组漂移增加的有害影响所推翻。此外，突变清除和漂移的相对强度关键取决于雄性交配性状的环境差异。具体来说，环境差异的增加导致更强的性选择，从而提高有害突变固定率和平均选择系数，推动漂移负荷的快速积累并减少种群持续时间。这些结果凸显了性选择对遗传负荷的相互冲突的积极和消极后果之间的复杂平衡，即使在没有性对抗选择的情况下也是如此。他们意味着关键交配特征的环境差异和内在遗传漂变应该适当地纳入未来关于性选择下种群适应性进化的理论和实证研究中。