Guest, Heidi J. , Allen, Geraldine A. .
Systematic and phylogeographic implications of molecular variation in the western North American roseroot Rhodiola integrifolia (Crassulaceae).
The roseroot genus Rhodiola, although most diverse in Asia, includes three species in North America. The arctic/alpine R. integrifolia occurs in western North America and northeastern Asia. We examined nuclear (ITS) and plastid (psbA-trnH spacer) DNA variation in this species and its North American relatives, R. rosea and R. rhodantha. Phylogenetic analyses based on ITS showed that (i) the western North American species R. integrifolia and R. rhodantha are distinct but closely related sister taxa; and (ii) these two species and the eastern North American R. rosea belong to separate clades within Rhodiola. Although the sister species R. integrifolia and R. rhodantha are distinct, some populations in the southern Rocky Mountains (where the two species overlap) shared plastid DNA haplotypes, suggesting that they hybridize. Within R. integrifolia, both nuclear and plastid DNA showed strong north-south geographic patterns, consistent with the glacial history of western North America. We sequenced the psbA-trnH spacer region in samples from 66 populations of R. integrifolia, and identified 28 cpDNA haplotypes. Of these, 16 haplotypes were found either exclusively within the Beringian refugium (unglaciated regions of Alaska and Yukon) or in Beringia and immediately adjacent regions. One haplotype occurred from eastern Alaska to central British Columbia. Two other haplotypes were very widely distributed, extending from the Yukon to California, and five haplotypes were found exclusively south of the glacial maximum. Two haplotypes were found only on the Queen Charlotte Islands and adjacent central coast of British Columbia, suggesting persistence in coastal refugial habitats. The available data suggest that R. integrifolia originated in Asia and dispersed eastward and southward into its present range. It appears to have persisted both north and south of the Cordilleran Ice Sheet during the last glacial advance, subsequently recolonizing deglaciated regions primarily from the north.
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1 - University of Victoria, Department of Biology, P.O. Box 3020 STN CSC, Victoria, British Columbia, V8W 3N5, Canada
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood C/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 9:30 AM