Dissertation Research: The Role of Selection in Diversifi- cation of Herbivorous Insects: An Analysis of Mechanism

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Species proliferation must occur through the evolution of reproductive isolation. However, few studies of evolutionary radiation explore the mechanisms by which biological innovations may facilitate speciation. The high diversities of the relatively few herbivorous insect taxa suggest that herbivory represents an innovation fostering radiation. Host-plant specialization, furthermore, may plausibly promote reproductive isolation, as host plants: 1) are patchily distributed, yielding geographic isolation, and 2) exert strong selection pressures, yielding adaptive divergence. The student will investigate speciation in the leaf-feeding beetle genus Neochlamisus. Three geographically isolated populations of N. bebbianae, two sharing the same host, will be the focus of microevolutionary study. The degree of reproductive isolation exhibited by the same-host population pair will be compared to that for a different-host pair for a variety of potential components of isolation. Greater observed isolation between the different-host populations would support the hypothesis that speciation is driven by selection rather than by random genetic drift. A DNA sequence-based phylogenetic study will be performed and use to infer host-associations of ancestral ferns.