Data from: Size-dependent selective mechanisms on males and females and the evolution of sexual size dimorphism in frogs

Sexual size dimorphism (SSD) varies in animals from male biased to female
biased. The evolution of SSD is potentially influenced by a number of
factors, such as territoriality, fecundity, and temporal breeding patterns
(explosive vs. prolonged). In general, frogs show female-biased SSD with
broad variance among species. Using comparative methods, we examine how
different selective forces affect male and female sizes, and we test
hypotheses about size-dependent mechanisms shaping SSD in frogs. Male size
was weakly associated with SSD in all size classes, and we found no
significant association among SSD, male size, temporal breeding pattern,
and male territoriality. In contrast, female size best explained SSD
variation across all size classes but especially for small-bodied species.
We found a stronger evolutionary association between female body size and
fecundity, and this fecundity advantage was highest in explosively
breeding species. Our data indicate that the fecundity advantage
associated with female body size may not be linear, such that intermediate
and large females benefit less with body size increases. Therefore,
size-dependent selection in females associated with fecundity and breeding
patterns is an important mechanism driving SSD evolution in frogs. Our
study underscores the fact that lineage-specific ecology and behavior
should be incorporated in comparative analyses of animal SSD.

动物界的性大小二态性（Sexual size dimorphism, SSD）存在广泛变异，覆盖雄性偏向与雌性偏向两种类型。性大小二态性的演化可能受多种因素影响，例如领地性、繁殖力以及繁殖时间模式（爆发式繁殖 vs 延长式繁殖）。总体而言，蛙类普遍呈现雌性偏向的性大小二态性，且不同物种间的变异幅度较大。本研究采用比较研究方法，探究不同选择压力如何作用于雌雄个体体型，并检验关于调控蛙类性大小二态性的体型依赖型机制的相关假说。在所有体型等级中，雄性体型与性大小二态性仅存在微弱关联；同时我们未发现性大小二态性、雄性体型、繁殖时间模式与雄性领地性之间存在显著关联。与之相反，雌性体型能够最佳解释所有体型等级下的性大小二态性变异，尤其在小型物种中这一效应更为显著。我们发现雌性体型与繁殖力之间存在更强的演化关联，且该繁殖力优势在爆发式繁殖的物种中表现最为突出。我们的数据表明，与雌性体型相关的繁殖力优势并非呈线性关系：中等体型与大体型的雌性个体，其繁殖力随体型增长所获得的收益相对更低。因此，与繁殖力及繁殖模式相关的雌性体型依赖型选择，是驱动蛙类性大小二态性演化的重要机制。本研究强调，在开展动物性大小二态性的比较研究分析时，应纳入物种谱系特异性的生态与行为特征。