Body size explains most of the variation in fitness within animal populations and is therefore under constant selection from ecological and reproductive pressures, which often promote its evolution in sex‐specific directions, leading to sexual size dimorphism (SSD). Several hypotheses have been proposed to explain the vast diversity of SSD across species. These hypotheses emphasize: (a) the mate competition benefits to larger male size (sexual selection); (b) the benefits of larger female size for fecundity (fecundity selection); (c) the simultaneous benefits of niche divergence for males and females to reduce intersexual competition for ecological resources (natural selection); and (d) the underlying impact of geographical variation in climatic pressures expected to shape large‐scale patterns of SSD in synergy with the above selection pressures (e.g., intensification of fecundity selection as breeding seasons shorten). Based on a new, global‐scale amphibian dataset, we address the shortage of large‐scale, integrative tests of these four hypotheses.

中文翻译：

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全球两栖动物性大小二态性的多种起源

身体大小可以解释动物种群中大多数健康状况的变化，因此需要不断从生态和生殖压力中进行选择，生态压力和生殖压力通常会促进其在特定性别方向上的进化，从而导致性大小二态性（SSD）。提出了几种假设来解释物种间SSD的巨大多样性。这些假设强调：（a）伴侣竞争有利于更大的男性尺寸（性选择）；（b）扩大女性规模对生育能力的好处（选择生育能力）；（c）利基差异对男性和女性的同时好处，以减少两性对生态资源的竞争（自然选择）；（d）与上述选择压力协同作用（例如随着繁殖季节的缩短，繁殖力的增强），预计地理压力对地理变化的潜在影响将影响SSD的大规模模式。基于一个新的，全球规模的两栖动物数据集，我们解决了这四个假设的大规模，综合检验的不足。