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 po...

若性选择与自然选择在不同性别中的作用存在分化，那么雌雄个体可能面临差异化的进化压力。由此，诸多物种演化出了性二色性（sexual dichromatism），即两性间的体色差异。尽管性二色性常被用作衡量性选择强度的指标，但该性状实则为复合性状。本研究以鸟类中规模最大、生态多样性最丰富的类群之一——唐纳雀科（tanagers）为研究对象，结合鸟类视觉视角与物种水平系统发育树，探究性二色性的演化历程。研究结果表明，性二色性的演化降低更多与雄鸟羽色的更大幅度、更频繁的变化相关；而性二色性的演化提升，则并未与任一性别的羽色更大幅度变化存在关联。此外，本研究还发现，雄鸟的冠部与腹部羽区与性二色性存在相关性，且仅雄鸟羽色复杂度为……