Data from: The role of sexual and natural selection in shaping patterns of sexual dichromatism in the largest family of songbirds (Aves: Thraupidae)

Males and females can be under different evolutionary pressures if sexual and natural selection is differentially operating in each sex. As a result, many species have evolved sexual dichromatism, or differences in coloration between sexes. Although sexual dichromatism is often used as an index of the magnitude of sexual selection, sexual dichromatism is a composite trait. Here, we examine the evolution of sexual dichromatism in one of the largest and most ecologically diverse families of birds, the tanagers, using the avian visual perspective and a species-level phylogeny. Our results demonstrate that the evolutionary decreases of sexual dichromatism are more often associated with larger and more frequent changes in male plumage coloration, and evolutionary increases are not more often associated with larger changes in either sex. Furthermore, we show that the crown and ventral plumage regions are correlated with sexual dichromatism in males, and that only male plumage complexity is positively correlated with sexual dichromatism. Finally, we demonstrate that light environment is important in shaping both plumage brilliance and complexity. By conducting a multilevel analysis of plumage evolution in males and females, we show that sexual dichromatism evolves via a mosaic of sexual and natural selection in both sexes.

当性选择与自然选择在雌雄两性间存在差异化作用时，两性可能面临不同的进化压力。由此，诸多物种演化出了性别色彩二态性（sexual dichromatism），即两性间的色彩差异。尽管性别色彩二态性常被用作衡量性选择强度的指标，但它实则是一种复合性状。本研究以鸟类中类群最丰富、生态多样性最高的类群之一——裸鼻雀科（tanagers）为研究对象，结合鸟类视觉视角与物种级系统发育树，探讨了性别色彩二态性的演化机制。研究结果显示，性别色彩二态性的进化降低事件，更多与雄鸟羽色发生更大幅度且更频繁的变化相关；而性别色彩二态性的进化提升事件，则并未与任一性别的羽色更大幅度变化存在关联。此外，我们发现雄鸟的头顶羽区与腹面羽区的色彩特征与性别色彩二态性存在相关性，且仅雄鸟的羽色复杂度与性别色彩二态性呈正相关。最后，我们证实光照环境对羽色的鲜亮程度与复杂度均具有重要塑造作用。通过对雌雄两性羽色演化开展多层次分析，我们揭示了性别色彩二态性是通过两性间性选择与自然选择的镶嵌式协同作用实现演化的。