Climate, habitat, and geographic range overlap drive plumage evolution
Organismal appearances are shaped by selection from both abiotic and biotic drivers 1-5. For example, Glogers rule describes the pervasive pattern that more pigmented populations are found in more humid areas 1,6,7, and substrate matching as a form of camouflage to reduce predation is widespread across the tree of life 8-10. Sexual selection is a potent driver of plumage elaboration 5,11, and species may also converge on nearly identical colours and patterns in sympatry, often to avoid predation by mimicking noxious species 3,4 To date, no study has taken an integrative approach to understand how these factors determine the evolution of colour and pattern across a large clade of organisms. Here we show that both habitat and climate profoundly shape avian plumage. However, we also find a strong signal that many species exhibit remarkable convergence not explained by these factors nor by shared ancestry. Instead, this convergence is associated with geographic overlap between species, suggesting strong, albeit occasional, selection for interspecific mimicry. Consequently, both abiotic and biotic factors, including interspecific interactions, are potent drivers of phenotypic evolution.