Behaviour 2019
Diverse selective pressures drive color and contrast evolution in wood-warblers
Richard K. Simpson, Allison F. Mistakidis, Stéphanie M. Doucet. University of Windsor, Windsor, ON, Canada

Natural and sexual selection drive the evolution of animal coloration. Variation in the visual environment can further influence color variation. However, these different selective forces are often studied independently or using proxies for selection. We evaluated the roles of natural and sexual selection on color evolution in 17 sympatric wood-warbler species using extra-pair paternity (EPP) and testes size to quantify sexual selection and brood parasitism and nest predation rates to estimate natural selection. We also assessed the influence of the visual environment. We tested the effects of each selective pressure on male and female warbler color and background contrast. Species with more colorful plumage experienced more brood parasitism, had higher EPP rates, and occupied habitats with greater canopy cover. Species with greater background contrast experienced more nest predation/parasitism, had higher EPP rates, and used lower perch heights with greater canopy cover. Our findings show how selection operates on both color and contrast and demonstrate the costs and benefits of increased conspicuousness. Our results illustrate how multiple selective factors drive color evolution.