Phylogeography of the plants disjunct between western North America and the Great Lakes Region : patterns, case studies, and implications for future comparative research

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Drummond, Chloe Pak, author

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Online

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Summary

More than 100 vascular plant taxa have a discontinuous geographic distribution between western North America and the Great Lakes Region. Each of these species is distributed in a pattern characteri...

More than 100 vascular plant taxa have a discontinuous geographic distribution between western North America and the Great Lakes Region. Each of these species is distributed in a pattern characterized by occurrence from Alaska south through the western Rocky Mountains, with reappearance in the Great Lakes Region, where they are often locally endangered. Some of these species have additional occurrences in the Black Hills of South Dakota. In this thesis I provide an updated review of this disjunct biogeographic pattern and presents three in-depth case studies of this geographic distribution: [Rubus parviflorus] Nutt. (Thimbleberry, Rosaceae), [Oplopanax horridus] (Sm.) Miq. (Devil's-club, Araliaceae), and [Aconitum columbianum] Nutt. (Columbian monkshood, Ranunculaceae). For each of these case studies I present 1) how old these species are and how their age supports or refutes different historical migration hypotheses that are centered around Pleistocene geological events, 2) the historical geographic range of these species and how they came to occupy their current distribution, and 3) population dynamics, such as bottlenecks and gene flow, that contribute to the genetic diversity of the Great Lakes Region populations. These analyses leverage geo-referenced specimen data and next-generation sequencing. They uncover different underlying phylogeographic histories between the case studies, indicating that this shared biogeographic pattern is a more complex, pseudoparallel pattern. The results have implications for future research on the western North America-Great Lakes Region disjunct plants as well as future conservation efforts in the Great Lakes Region.

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