DISSERTATION RESEARCH: Tests of parallel divergence processes in montane plants: links between population differentiation and species diversity patterns

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How did the cyclical advance and retreat of glaciers affect biodiversity within mountainous regions? How do environmental gradients and geography influence the current structure of diversity within species across their ranges? Researchers will address these questions by utilizing hundreds of DNA sequences from six closely related plant species native to the mountains of western North America. Analytical modeling techniques will allow them to determine if speciation events occurred uniformly among pairs of sister species or if they occurred under a variety of different scenarios. Subsequently, researchers will determine if glaciations that dramatically altered montane landscapes and suitable habitat during the Pleistocene Epoch (from 2,600,000 to 20,000 years ago) impacted species? distributions randomly or predictably. Finally, researchers will investigate if the current molecular variation within each of the species is distributed along environmental gradients (for example, the change in temperature between a valley floor and a mountaintop), by geography, or from the shifting of habitats during glaciations. Knowledge gained from these analyses will help researchers understand how biodiversity was created in the mountains. It will also help elucidate the relative importance of climatic stability versus specific environmental and geographic conditions in structuring the distribution of molecular diversity within species.Organisms living in montane ecosystems are facing an uncertain future as climate change alters temperature and precipitation regimes. Many montane organisms will be forced to move upslope as lower elevations become warmer and drier, and organisms already restricted to the highest elevations may die off because suitable habitat will no longer exist. Knowing what environmental variables influence the distributions of plants across the landscape will allow land managers and conservationists to counteract declines in species? population sizes. This research will inform professionals about how habitat suitability will change across the landscape, and help them to determine from where to source plant material in order to have the best results for reintroduction or assisted migration efforts. In summary, the results will contribute information relevant to preserving biodiversity across montane landscapes by highlighting how individual species are sensitive to different environmental conditions.