| Summary: | Recent molecular phylogenetic analyses have clearly shown the large, arctic and northtemperate genus Saxifraga (Saxifragaceae) sensu lato is polyphyletic with two distinct clades: Saxifraga sensu stricto and Micranthes. Six species belonging to Micranthes exist in the Southern Appalachians, including two questionably distinct species and one rock outcrop endemic. Taxonomists have traditionally distinguished the very similar M. careyana and M. caroliniana primarily based on geographic locality and four morphological characters: sepal orientation (erect or reflexed), filament shape (uniform or club-shaped), petal coloration (none or 2 yellow spots), and fruit length (2.5-5 or 4-5 mm). The goal of this research was to examine these characters to clarify the taxonomy of these species and look for molecular differences in the nuclear and chloroplast DNA regions, and examine the phylogeny of all six Southern Appalachian species in the context of the entire genus. Several populations of M. careyana and M. caroliniana from the Blue Ridge Physiographic Province have been examined and material has been collected for molecular analyses. Populations in the counties of Ashe, Alleghany, and Watauga (North Carolina) and Johnson (Tennessee) displayed reflexed sepals and clubshaped stamen filaments, consistent with M. caroliniana. Populations examined in flower in all other counties displayed erect sepals and uniform stamen filaments, consistent with M. careyana. The other two characters were not useful in distinguishing these taxa. These differences in floral characters are correlated with mutations in ITS and trnL-F sequences. In phylogenetic analyses, populations determined to represent M. caroliniana appear in a distinct clade from those determined to represent M. careyana, supporting the separation of the two as species. In addition, the high-elevation rock outcrop endemic M. petiolaris appears in a distinct clade from the other five Southern Appalachian species, indicating this taxon evolved along a separate lineage and ...
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