DISSERTATION RESEARCH: Hormonal Regulation of Feather Color Development and Variation across Populations

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Bird feathers are one of the most striking examples of diversity on the planet. The color and shape of feathers are of fundamental importance in bird courtship rituals, camouflage, and other social and ecological interactions. Feathers can evolve rapidly - populations of the same species often show striking differences in feather color and patterns. The mechanisms that are responsible for these differences, however, are poorly understood. Abolins-Abols investigates how and why feather color differs between individuals and populations. In this dissertation improvement project Abolins-Abols will investigate the hormonal mechanisms that regulate the development of two rapidly evolving feather traits - head and tail color - across multiple populations of the Dark-eyed Junco, a small songbird that is a common visitor to feeders across the United States. This research will increase our understanding of the evolution of bird color diversity, because head and tail feathers are hotspots for variation across songbirds. This project will also train undergraduate students and facilitate outreach to the general public using the newly founded bird banding station where Abolins-Abols will characterize color variation across a variety of migratory bird species. The affordability and simplicity of this study system make it a prime candidate for future research programs in development and evolution, especially at smaller institutions such as liberal arts colleges.Some feather ornaments are used as honest signals, suggesting that their development is integrated with other phenotypic traits such as behavior. A candidate mechanism for this integration is hormones, which regulate both neural and peripheral processes. While hormones have been shown to mediate sex differences coloration, we do not yet understand the role of hormones in mediating individual differences and population divergence in feather color. Abolins-Abols proposes to investigate the genetic and hormonal mechanisms that mediate the development of two rapidly evolving social plumage ornaments - head and tail color in Dark-eyed Juncos - across populations of varying coloration. These honest feather ornaments have been shown to be related to individual differences in testosterone physiology, suggesting a causal link between hormones and feather color. To gain an explicit understanding of whether and how hormones regulate this variation, Abolins-Abols will analyze hormone receptor gene and protein expression in developing feathers in combination with experimental manipulations of testosterone and luteinizing hormone. By understanding the hormonal regulation of these ornaments we will gain insight into how these ornaments are linked to behavior as well as a better understanding of how hormones mediate the divergence of social feather ornaments.