The evolution of sexual dichromatism in a large radiation of landfowls: re-examining the female-biased selection in Wallace’s model

Sexual dichromatism, the colour difference between males and females, has been particularly important for studying the interplay between sexual and natural selection. However, previous studies on the evolutionary forces of sexual dichromatism examing the Darwin’s and Wallace’s model have produced mixed results. Phasianidae is a species-rich family with worldwide distribution, occupancy in nearly all terrestrial habitats, and a wide diversity of plumage patterns and colourations. Here, we use phylogenetic comparative methods to test the relationship between sexual dichromatism and colour complexity of males and females on both evolutionary direction and tempo including all species in Phasianidae. We show that the evolutionary direction of sexual dichromatism is negatively correlated with colour complexity in females but not males, and the evolutionary rates of sexual dichromatism are positively correlated with the evolutionary rates of colour complexity in both sexes. These results highlight the important role of female colour evolution in shaping sexual dichromatism in the pheasant family, and provide strong empirical supports for Wallace’s hypothesis via a mosaic of sexual and natural selection in both sexes. ### Competing Interest Statement The authors have declared no competing interest.