DISSERTATION RESEARCH: Female ornamentation in the White-shouldered Fairywren: Proximate mechanisms and adaptive function

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Showy traits, or ornaments, have long captured the imagination of naturalists and evolutionary biologists. One theory of selection provides a robust explanation for variation in male coloration, or ornamentation, through the process of females choosing increasingly elaborate males over numerous generations. In contrast, the evolution of female ornamental coloration has received comparatively little attention, and is not intuitively explained using current theory. The White-shouldered Fairywren (Malurus alboscapulatus) of New Guinea is an unusual species of bird in which female coloration varies across populations, while male plumage remains constant. Experimental evidence suggests that more ornamented coloration in females is associated with heightened aggression and increased levels of testosterone. However, the connection between behavior and the underlying process that has led to the appearance of female ornamentation in this species remain unclear. This research aims to determine what genes are responsible in male and female fairywrens for producing ornamentation. The research addresses a core goal in evolutionary biology in identifying the underlying mechanisms that are responsible for generating specific appearances, but from a uniquely female-perspective approach. Understanding the processes involved in generating patterns of biodiversity will be communicated to local communities at our study sites in New Guinea and to local school aged children in New Orleans. A contemporary goal of evolutionary biology is to understand the genomic changes that control phenotypic variation and how genomic variation generates diversity in traits. The investigators will use high throughput sequencing techniques to explore the underlying genetic control of plumage variation in the White-shouldered Fairywren. They have two complementary goals: to use whole genome resequencing to identify regions of the genome that may be under selection and to use RNA sequencing to test for differences in gene expression between distinct female phenotypes. The study will advance the understanding of the evolution of sex-specific coloration by testing hypotheses for how changes in female ornaments may arise on a mechanistic level, which can then be contextualized with data the researchers have gathered on current adaptive function of the trait. The strength of this system is that it presents an opportunity to compare variation in female ornaments, rather than the more commonly observed and better studied variation in male traits. Female ornaments are influenced not only by selective forces acting on the traits, but also by the genetic mechanisms that produce the phenotype. The proposed genetic work will build on prior research in this species to provide a broad understanding of the evolution and function of female ornamentation that integrates field observation, experimental manipulation, and laboratory techniques. In doing so, the research is expected to provide a comprehensive understanding of both the proximate basis for and ultimate consequences of elaborate female coloration.