Relationships of Eastern North American Phlox (Polemoniaceae) based on ITS sequence data

Abstract

Phylogenetic relationships of eastern Phlox (Polemoniaceae) are examined using sequence data from the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA. Eastern North American Phlox species have been the focus of many evolutionary studies, and hybridization is thought to have played a role in the origin and evolution of some taxa. The phylogenetic information presented here leads to several important conclusions relevant to taxonomy, notably that Wherry's sections Phlox and Annuae are not monophyletic, and that the eastern mat-forming taxa and the annuals of central Texas each form monophyletic groups. Neither of the two large species complexes in the east, the P. pilosa complex and the P. glaberrima complex, is monophyletic in the ITS tree. While the tree is consistent with a history of hybridization, the ITS data do not directly support previous hypotheses of hybrid origin of particular taxa.