Molecular Phylogeny and Comparative Pollen Morphology of the Genus Hexastylis (Aristolochiaceae)

Asarum, commonly known as wild ginger, heartleaves, or little brown jugs, is a genus belonging to the family Aristolochiaceae. Asarum exhibits a Laurasian distribution, with species in Europe, Asia, and North America. Of particular interest to this study is the genus Hexastylis. Recent studies showed that Hexastylis is rooted within Asarum and suggested to be paraphyletic, but failed to adequately examine relationships within this southeastern United States complex of species. The genus, as currently understood, consists of nine species and four varieties. Pollen was examined for all currently recognized Hexastylis taxa. Although pollen analysis showed similar surface features for most taxa, some variation in morphology became visible under increased magnification. One species, Hexastylis naniflora lacked some surface features present in the other taxa. There is currently no robust molecular analysis of relationships within the genus. Three chloroplast regions were sequenced to resolve the relationships. We have sequenced both genes for twenty taxa including ingroups and outgroups. Genetic information was analyzed using Bayesian, Parsimony, and Maximum Likelihood methods. Contrary to a prior study, Hexastylis was found to be monophyletic as indicated by a 6 bp insertion.