Insights into eyespots: Gene expression and function in the development of butterfly wing color patterns
Ramos, Diane Marie
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The eyespot color patterns of the butterfly, Bicyclus anynana , have become an important system in which to examine the developmental basis of evolutionary novelties. Many candidate genes have been screened, based upon their known roles in Drosophila wing development, and found expressed in novel locations, which implicate the gene products in the development of eyespot patterns. The lack of causational evidence for the involvement of these candidate genes, however, has meant that our understanding of eyespot development remains incomplete. This dissertation builds upon the recent generation of germ-line transformation in B. anynana to provide the first test of gene function in eyespot development in this species. By inducing ubiquitous expression of the transcription factor, spalt , I show that spalt has a role in specifying the location of two veins as well as a role in determining eyespot size. In addition to the ubiquitous expression approach, I present a method to test spatially restricted gene expression using laser-mediated heat shock. This method drives gene expression in complex patterns on the pupal wing epidermis without causing significant cell death. Finally, I show that the genome of B. anynana contains three members of the engrailed/invected gene family that are expressed in a combination of both overlapping and unique patterns in the pupal wing. These expression patterns provide insight into the evolution of the development of eyespots in the Bicyclus lineage. Taken together, the research presented in this dissertation contributes to our efforts to understand primarily the development but also the evolution of a morphological novelty.