Dissertation Research: Functional Genomics of Ornament Production in a Warbler

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Ornamental traits, such as the long tails and bright colors of some birds, are thought to be honest indicators of male quality to potential mates, because only males with relatively more resources can afford to produce them. However, in some cases the energetic cost of producing an ornament does not appear to be large, and, thus, it is not clear what limits individuals from producing elaborate ornaments. In common yellowthroats (Geothlypis trichas) males with larger black facial masks are preferred as mates by females, yet producing the color of the mask feathers is not thought to be costly. In this project, the researchers will examine the physiological processes associated with producing larger black ornaments by studying the expression of genes in developing ornamental (facial mask) and non-ornamental (back) feathers. The goal of this research is to test three hypotheses that predict which genes are of importance during the development of ornaments and, thus, determine what information these ornaments are signaling to potential mates. A deeper understanding of feather development will also be of interest to other disciplines, including those concerned with avian disease and husbandry. The researchers will share the results of this study through public presentations at local nature centers, in addition to presentations at scientific conferences and publications in peer-reviewed journals. The production of elaborate ornaments selected through mate choice is likely affected by the expression of genes involved in important physiological processes. Genes that may be of particular importance during ornament development include those involved in oxidative phosphorylation (OXPHOS hypothesis), immune function (Hamilton and Zuk hypothesis), and growth (e.g., insulin and insulin-like growth factor genes; insulin/IGF hypothesis). In common yellowthroats the black facial mask is thought to honestly signal male quality because mask size is positively related to immune gene (MHC class II) variation, antibody production, and resistance to oxidative stress. In this study, researchers will use RNA-sequencing to determine if genes involved in important physiological functions (e.g., OXPHOS, immune, insulin/IGF) are more highly expressed in developing feathers that form part of a sexually selected ornament (the mask) than those from other non-sexually selected parts of the plumage (the back). This research will provide the first comparison of transcriptomes of developing ornamental and non-ornamental feathers.