Size differences between males and females are common across the tree of life (termed sexual size dimorphism; SSD), and have fundamental implications for ecology, life history and behaviour of both sexes. Conventionally, SSD is thought to evolve in response to sex‐specific sexual selection but more recent work suggests that ecological processes can also promote sex‐differences in size. Here, we provide a global test for the role of sexual selection in the evolution of sexual size dimorphism using data from 77 comparative studies spanning the major classes of the animal kingdom. We show that intense sexual selection typically correlates with male‐biased SSD across species. Importantly, pre‐copulatory but not post‐copulatory sexual selection predicts SSD, suggesting a pervasive role of premating male–male competition and female choice to drive sex differences in body size. Collectively, our findings suggest that pre‐copulatory sexual selection plays a major role in the evolution of male‐biased SSD.

中文翻译：

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交配前性选择预测性大小二态性：比较研究的荟萃分析


雄性和雌性之间的大小差异在生命之树中很常见（称为性大小二态性;SSD），并对两性的生态、生活史和行为具有根本影响。传统上，SSD 被认为是为了响应性别特异性的性选择而进化的，但最近的研究表明，生态过程也可以促进大小的性别差异。在这里，我们使用来自动物界主要类别的 77 项比较研究的数据，为性选择在性大小二态性进化中的作用提供了全球测试。我们表明，强烈的性选择通常与跨物种的雄性偏向 SSD 相关。重要的是，交配前而非交配后性选择可预测 SSD，这表明雄性竞争和女性选择在驱动体型性别差异方面具有普遍作用。总的来说，我们的研究结果表明，交配前性选择在男性偏倚 SSD 的进化中起着重要作用。