DISSERTATION RESEARCH: Colonization History and Genetic Structure of Incipient Sexual Isolation Between USA and Caribbean Populations of Drosophila Melanogaster

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This study addresses fundamental questions concerning how humans may alter the evolutionary history and biology of human-associated species. In a time when humans are constantly expanding the geographical ranges of species all over the world, very little is known about how this will affect the genetic and phenotypic constitution of species. Cases in which species expanded their ranges due to human transport resulting in the first stages of reproductive isolation (race formation) are rarely described or well characterized. Research on the fruit fly Drosophila melanogaster in the Caribbean islands offers an unprecedented opportunity to study just such a case. This is because it is hypothesized that this African species colonized the Caribbean as a result of historical African slave trades. The study will provide insight into how a species range expansion leads to behavioral isolation between ancestral and derived populations. The research will determine whether the observed morphological, pheromonal and behavioral differences between United States and Caribbean fly populations are due to either: 1) distinct colonization events, the U.S. flies being colonized from Europe in the 1800s and the Caribbean flies being colonized from Africa during the 1600s slave trades, or 2) U.S. flies colonizing the Caribbean and subsequently adaptively converging onto African-like tropical traits. This research will also pave the way toward future work on the identification of genes responsible for the observed phenotypic divergence and sexual isolation.This project will have substantial broader impacts in addition to its intellectual impacts. The research will continue to involve both undergraduates and high school students. Seven undergraduates (including one under-represented minority member and four women) are presently working on this project and are expected to be co-authors of future publications. This past summer a high school student finished second place nationwide in the prestigious Siemens-Westinghouse Science Competition (2005-2006) for their research on this project. Principal Investigator True uses the Bahamas flies extensively in teaching an undergraduate Molecular Diversity Laboratory course. Finally, contacts have been established with biologists in the Department of Agriculture in Nassau, Bahamas, which will facilitate a greater exchange of ideas between the United States and Bahamian academic communities.