Phylogeny of the North American Rhodiola based on Chloroplast DNA Sequence Data

Plants in the genus Rhodiola are perennial herbs that grow in alpine and arctic regions of Eurasia and North America.  Some are used in traditional medicines, and some, such as the North American Rhodiola integrifolia ssp. leedyi, (Leedy’s roseroot) are rare.  Recent studies that have been called for by the U.S. Fish and Wildlife Service suggest that the most widely used taxonomic treatment does not accurately reflect the group’s evolutionary history.  To test Leedy’s roseroot’s relationships with the other North American Rhodiola taxa we are analyzing the nucleotide sequence of the chloroplast DNA trnL-F region.  We have successfully amplified this marker in 71 individuals representing all of the known North American Rhodiola taxa, and obtained preliminary sequence data from 3 individuals. Our preliminary results suggest that 4 nucleotide differences exist between Leedy’s roseroot and its closest relatives (R. integriofolia ssp. integrifolia, ssp. procera, and ssp. neomexicana), and that there is a difference of 65 nucleotides from its most distant North American relative.  These findings suggest that the trnL-F region will be informative for reconstructing the evolutionary relationships, and that Leedy’s roseroot is a distinct species.  We will present trnL-F sequence data from approximately 50 individuals representing all of the North American Rhodiola taxa, and interpret the data in light of other evolutionarily relevant information on the taxon.  Our results will inform management and conservation practices for Leedy’s roseroot and contribute to the orderly investigation of Rhodiola species for medicinal purposes.