Sexual size dimorphism (SSD) is shaped by multiple selective forces that drive the evolution of sex-specific body size, resulting in male or female-biased SSD. Stronger selection on one sex can result in an allometric body-size scaling relationship consistent with Rensch's rule or its converse. Anurans (frogs and toads) generally display female-biased SSD, but there is variation across clades and the mechanisms driving the evolution of SSD remain poorly understood. We investigated these topics in a diverse family of African treefrogs (Hyperoliidae). Hyperoliids display traits considered rare among amphibians, including sexual dichromatism and protogynous sex change. Using phylogenetic comparative methods, we tested if adult ecology, sexual dichromatism, and sex change were predictors of body size or SSD. We also tested whether hyperoliids displayed allometric interspecific body-size-scaling relationships. We found a majority of hyperoliid taxa display female-biased SSD, but that adult ecology and sexual dichromatism are poor predictors of sex-specific body size and SSD. Regardless of the groupings analyzed (partitioned by clades or traits), we found support for isometric body-size scaling. However, we found that sex change is a significant predictor of SSD variation. Species in the Hyperolius viridiflavus complex, which putatively display this trait, show a significant reduction in SSD and are frequently sexually monomorphic in size. Although protogynous sex change needs to be validated for several of these species, we tentatively propose this trait is a novel mechanism influencing anuran body size evolution. Beyond this association, additional factors that shape the evolution of anuran body size and SSD remain elusive.

中文翻译：

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非洲树蛙（科：Hyperoliidae）性别大小二态性的宏观进化模式

性别大小二态性 (SSD) 是由多种选择力塑造的，这些力量推动了性别特定体型的演变，从而导致 SSD 偏向男性或女性。对一种性别的更强选择可以导致与伦施规则或其相反的异速生长的身体大小比例关系。Anurans（青蛙和蟾蜍）通常表现出偏向女性的 SSD，但进化枝之间存在差异，并且驱动 SSD 进化的机制仍然知之甚少。我们在不同种类的非洲树蛙（Hyperoliidae）中调查了这些主题。Hyperoliids 显示出在两栖动物中被认为罕见的特征，包括性二色性和原雌性变性。使用系统发育比较方法，我们测试了成人生态学、性二色性和性别变化是否是体型或 SSD 的预测因子。我们还测试了 hyperoliids 是否显示异速生长的种间大小比例关系。我们发现大多数 hyperoliid 分类群显示出女性偏向的 SSD，但成体生态学和两性二色性是性别特异性体型和 SSD 的不良预测指标。无论分析的分组如何（按进化枝或特征划分），我们都发现支持等距体型缩放。然而，我们发现性别变化是 SSD 变异的重要预测因素。Hyperolius viridiflavus 复合体中的物种，假定显示出这种特征，显示出 SSD 的显着减少，并且通常在大小上是性单形的。尽管需要验证其中几个物种的原始性别变化，但我们暂时提出这种特征是影响无尾猿体型进化的新机制。除了这个协会，