The Molecular Costs of Being Sexually Attractive: a Quantitative Assessment of Carotenoid Limitations for Coloration and Self-Maintenance

Arizona State University, Scottsdale AZ

Investigators

Abstract

For centuries, biologists have been captivated by exaggerated features in animals (i.e. elongated horns in deer, elaborate bird songs). Evolutionary theory predicts that these 'ornaments' are costly to produce and thus serve as reliable indicators of an individual's worth to potential mates or rivals. Despite several decades of research on animal communication, the true intrinsic, molecular costs that go into producing such signals are poorly established. The investigators will use comparative nutritional, biochemical, immunological, and morphological approaches to investigate the costs of producing a common exaggerated trait in birds: ornate carotenoid-based plumage coloration. In many bird species, the most brightly colored individuals are preferred as mates. Yellow-to-red carotenoid coloration of feathers requires pigments obtained from food (like in tomatoes and corn), but these same pigments are also valuable for self-maintenance (i.e. antioxidant defense, immunomodulation). This potential trade-off in use of carotenoid pigments is optimal for testing how nutrient limitations dually govern the sexual trait expression and health quality of individuals. The investigators will study carotenoid intake, allocation, and coloration in wild birds growing their colorful feathers as well as in captive birds fed diets varying systematically in carotenoid content. They will use five pairs of closely related bird species (i.e. blackbirds, sparrows, ducks), one of which shows carotenoid coloration and the other of which does not, in order to test predictions about how carotenoids are apportioned under varying acquisitional and utilizational demands. This research will contribute to valuable bodies of work on antioxidants and health in humans and domestic animals. Results will be published in scientific and layperson (e.g. magazines) forums to foster scientific learning among broader audiences. Undergraduate, minority, and youth scholars within our institutions and communities will be trained in diverse fields. Fieldwork on colorful backyard birds will stimulate collaborations and information sharing with the public.