Reproductive Isolation in Drosophila

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Biology | Life Sciences


Charles Rodell, Biology


Speciation, the process by which new species arise, is not well understood. Even less is known about the underlying genetics of this process. My study examines the level of pre-mating and post-mating reproductive isolation among four closely related species of the Drosophila melanogaster group: D. melanogaster, D. simulans, D. mauritiana, and D. sechellia. Biological species are defined as populations that are reproductively isolated from other such populations. The emphasis of this definition is on reproduction, in that groups that are reproductively isolated from one another are not sharing genetic information and, hence, they are pursuing independent evolutionary paths. The isolation process can express itself at a range of levels. Theory predicts that pre-mating isolation occurs first, and is more prominent in populations that are sympatric. in order to test this prediction, I culture single-pair matings for all inter-specific crosses (test) and intra-specific crosses (control). The production of larvae (fertility) and adult offspring (viability) are used to measure post-mating isolation, and the successful transfer of sperm (mating) is used as a measure of pre-mating isolation.