Systematic Implications of DNA Restriction Site Variation inHymenoxysandTetraneuris(Asteraceae, Helenieae, Gaillardiinae)

Abstract

Generic delimitation in the Hymenoxys complex has long been problematic. One taxonomic extreme would recognize only Hymenoxys, whereas the other would split the obviously related taxa into as many as eight genera. This study examined restriction site variation in both cpDNA and nrDNA in the Hymenoxys complex. Fifty-six populations representing 21 species (four with two varieties each) and six of the eight possible genera were analyzed using 21 enzymes, which resulted in the detection of 358 restriction site changes of which 171 were potentially phylogenetically informative. Wagner parsimony using synapomorphic characters generated 26,600 equally parsimonious trees of 223 steps with a consistency index of 0.76 and a retention index of 0.98. Bootstrap analysis indicated that the major clades were strongly supported. The DNA tree supports the recognition of Tetraneuris as a genus separate from Hymenoxys, and the inclusion in Hymenoxys of taxa that at times have been split into the genera Dugaldia, Macdougalia, Phileozera, Picradenia, and Plummera.