Biogeography, systematics, and conservation genetics in the mountain snail group Oreohelix (Oreohelicidae)

Historical biogeography, in its broadest sense, is the study of the distribution and diversity of lineages, past and present, over the changing face of the Earth. The challenge for historical biogeographers remains to infer both the order and timing of lineage diversification events and the direct relation of these events to changes in environments. Snails in the genus Oreohelix (the mountain snail) are ideally suited for biogeography studies because of their broad distribution in the subalpine regions of the Western United States, their low adult migration, their lack of a high dispersal larval stage, and a low likelihood of passive transport by other animals. In the course of my dissertation work, I addressed the following three areas: (1) The taxonomic issues within Oreohelix; (2) The biogeographic history of and the conservation status for the most threatened Oreohelix species, O. cooperi and O. peripherica wasatchensis; and (3) The patterns and mechanisms of population genetic structure in a widespread species, O. strigosa. To address these topics, I utilized molecular data (mtDNA), ecological niche modeling data, and morphological data. Results show that the morphology-based taxonomy of Oreohelix is inaccurate, which led to taxonomic rearrangements across the genus. Through broad sampling in undocumented areas, a new species of Oreohelix, O. thermalis, was discovered and described. Phylogenetic and ecological niche modeling data provide some insight into the historical biogeography of the genus as well as potential connections between isolated endemic and widespread Oreohelix groups. We suggest that the ranges of two species, O. cooperi and O. peripherica wasatchensis, are larger than previously reported, implying that the conservation status of these groups may need revision. We also found cryptic species, which had previously been undocumented because of convergence in shell characters. Finally, using phylogenetic and ecological niche modeling data, we infer that gene flow between genetically and geographically isolated populations of the widespread O. strigosa are likely the result of passive, long-distance dispersal events.