Dissertation Research: Effect of Evolutionary History on Reproductive Isolation

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Biologists have long sought to discover how one species can evolve into two species, a process known as speciation. Some have argued that adaptation to different environments drives the evolution of new species, which is called ecological speciation. Others propose that speciation involves evolutionary change that is not related to environmental adaptation, which can be called null speciation This study will use long-isolated laboratory populations of the fruit fly, Drosophila melanogaster, some showing incipient speciation. Groups of these populations have been kept in identical environments, with some groups adapted to different ecological regimes. This is an ideal system for testing both null and ecological speciation. Mates that come from different populations produce offspring called hybrids. The inability to produce hybrids that are viable and fertile provides a measure of incipient speciation between two populations. Studying hybrids between many lab populations, some ecologically differentiated and some not, will test quantitatively which of the two speciation mechanisms, ecological or null respectively, is relatively more important.In addition to its fundamental importance for evolutionary biology, this research also has agricultural significance, because it will suggest how readily long-separated plant varieties and animal breeds can be hybridized to yield useful new agricultural stocks. The project will also provide opportunities for several undergraduate students to participate in scientific research.