Sexual dimorphism in life history traits and their trade‐offs is widespread among sexually reproducing animals and is strongly influenced by the differences in reproductive strategies between the sexes. We investigated how intrasexual competition influenced specific life history traits, important to fitness and their trade‐offs in the outcrossing nematode Caenorhabditis remanei. Here, we altered the strength of sex‐specific selection through experimental evolution with increased potential for intrasexual competition by skewing the adult sex ratio towards either females or males (1:10 or 10:1) over 30 generations and subsequently measured the phenotypic response to selection in three traits related to fitness: body size, fecundity and tolerance to heat stress. We observed a greater evolutionary change in females than males for body size and peak fitness, suggesting that females may experience stronger net selection and potentially harbour higher amounts of standing genetic variance compared to males. Our study highlights the importance of investigating direct and indirect effects of intrasexual competition in both sexes in order to capture sex‐specific responses and understand the evolution of sexual dimorphism in traits expressed by both sexes.

中文翻译：

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雌性和雄性线虫的实验诱导的性内交配竞争和性别特异性进化

生活史特征的两性二态性及其权衡在有性繁殖动物中很普遍，并且受到两性生殖策略差异的强烈影响。我们调查了性内竞争如何影响特定的生活史特征，这对健康及其在异交线虫 Caenorhabditis remanei 中的权衡很重要。在这里，我们通过实验进化改变了性别特异性选择的强度，通过将成年性别比例向雌性或雄性（1:10 或 10:1）倾斜超过 30 代来增加性内竞争的潜力，然后测量对选择与健康相关的三个特征：体型、繁殖力和对热应激的耐受性。我们观察到女性在体型和峰值适应性方面的进化变化大于男性，这表明与男性相比，女性可能会经历更强的净选择，并可能具有更高的遗传变异量。我们的研究强调了调查性内竞争对两性的直接和间接影响的重要性，以捕捉性别特异性反应并了解两性表达的性状中两性异形的演变。