| Phlox is a predominantly North American genus of subshrubs and herbs which has intrigued botanists for many decades. The group is well-known for hybridization--some species hybridize in nature and much evidence suggests several taxa arose via ancient hybridization. Despite the interest in Phlox and its value as an experimental system in evolutionary studies, a phylogenetic framework has been lacking. The primary goals of this research were to develop molecular phylogenies for eastern Phlox and to consider the possible effects of hybridization on those relationships. Sampling of eastern Phlox, particularly the P. pilosa L. complex, was extensive. Two phylogenies were generated, one based on the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA, and the second on chloroplast DNA restriction site data. Strong agreement between the independent phylogenies in several respects leads to clear taxonomic conclusions. Most notably, two sections recognized by Wherry (1955) are not monophyletic, the eastern mat-forming taxa represent a monophyletic group, and the central Texas annuals, P. cuspidata, P. drummondii and P. roemeriana, are closely related. The most fascinating aspect of the phylogenies, however, is the strong incongruence between them. Comparisons do suggest that hybridization has had a major effect on relationships of many eastern taxa. However, the relationships appear complicated and raise many further questions regarding particular taxa. Finally, molecular methods were also employed to investigate one case of current hybridization. Overall, these data are exciting because they provide another perspective on a wealth of previous studies and also point to promising areas of future research. |
