XVI International Botanical Congess

With ca. 700 species and a fossil record dating from the early Carboniferous, the Selaginellaceae are one of the oldest and most diverselineages of vascular land plants. Recent phylogenetic studies have demonstrated the utility of rbcL sequence data for resolving relationshipswithin this cosmopolitan, species-rich lineage. These data have providedstrong support for the monophyly of S. subg. Tetragonostachys, a group of ca.50 taxa that are found from widely disjunct localities in North and South America, Africa, India and Asia. Molecular data also indicate that the isophyllous S. subg. Tetragonostachys originated from an anisophyllous ancestor. Within the subgenus, moderate support is exhibited for two clades, corresponding to sections Eremophilae and Arenicolae. The phylogeny suggests that the distribution of S. subg. Tetragonostachys is the result of vicariance, and that the current diversity within Selaginella resulted from a combination of both ancient and recent speciation events.