Data from: Sexual dichromatism drives diversification within a major radiation of African amphibians
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Theory predicts that sexually dimorphic traits under strong sexual selection, particularly those involved with intersexual signaling, can accelerate speciation and produce bursts of diversification. Sexual dichromatism (sexual dimorphism in color) is widely used as a proxy for sexual selection and is associated with rapid diversification in several animal groups, yet studies using phylogenetic comparative methods to explicitly test for an association between sexual dichromatism and diversification have produced conflicting results. Sexual dichromatism is rare in frogs, but it is both striking and prevalent in African reed frogs, a major component of the diverse frog radiation termed Afrobatrachia. In contrast to most other vertebrates, reed frogs display female-biased dichromatism in which females undergo color transformation, often resulting in more ornate coloration in females than in males. We produce a robust phylogeny of Afrobatrachia to investigate the evolutionary origins of sexual dichromatism in this radiation and examine whether the presence of dichromatism is associated with increased rates of net diversification. We find that sexual dichromatism evolved once within hyperoliids and was followed by numerous independent reversals to monochromatism. We detect significant diversification rate heterogeneity in Afrobatrachia and find that sexually dichromatic lineages have double the average net diversification rate of monochromatic lineages. By conducting trait simulations on our empirical phylogeny, we demonstrate our inference of trait-dependent diversification is robust. Although sexual dichromatism in hyperoliid frogs is linked to their rapid diversification and supports macroevolutionary predictions of speciation by sexual selection, the function of dichromatism in reed frogs remains unclear. We propose that reed frogs are a compelling system for studying the roles of natural and sexual selection on the evolution of sexual dichromatism across both micro- and macroevolutionary timescales.
理论预测，处于强性选择作用下的两性异形性状，尤其是参与两性间信号交流的性状，能够加速物种形成并引发多样化爆发。性双色性（sexual dichromatism，即颜色层面的两性异形）被广泛用作性选择的替代指标，且在多个动物类群中与快速多样化相关联；然而，利用系统发育比较方法明确检验性双色性与多样化之间关联的研究却得出了相互矛盾的结果。性双色性在蛙类中较为罕见，但在非洲苇蛙中却既醒目又普遍——非洲苇蛙是名为Afrobatrachia的多样化蛙类演化辐射支系的核心组成类群。与绝大多数其他脊椎动物不同，苇蛙呈现出雌性偏倚的性双色性：雌性个体会发生体色转变，其体色通常比雄性更为华丽繁复。本研究构建了Afrobatrachia的高支持率系统发育树，以探究该演化辐射支系中性双色性的演化起源，并检验性双色性的存在是否与净多样化速率提升相关联。我们发现，性双色性在苇蛙科（Hyperoliidae）中仅演化出现一次，随后又发生了多次独立的逆转，回归到单色性状态。本研究在Afrobatrachia中检测到了显著的多样化速率异质性，且发现两性异形支系的平均净多样化速率是单色支系的两倍。通过在经验系统发育树上开展性状模拟实验，我们证实了关于性状依赖型多样化的推论具有稳健性。尽管苇蛙科的性双色性与其快速多样化存在关联，且支持性选择驱动物种形成的宏观演化预测，但苇蛙中性双色性的具体功能仍不明确。我们提出，苇蛙是一个极具研究价值的实验系统，可用于在微观演化和宏观演化的时间尺度上探究自然选择与性选择在性双色性演化中所发挥的作用。
