Phylogeny and Generic Circumscriptions of Cheilanthoid Ferns (Pteridaceae: Cheilanthoideae) Inferred from rbcL Nucleotide Sequences

Nucleotide sequences of the chloroplast DNA gene rbcL were determined for 25 species of cheilanthoid ferns (Pteridaceae subfamily Cheilanthoideae). Together with GenBank sequences of an additional cheilanthoid and a 14-species outgroup comprising Pteridaceae, Vittariaceae, and Coniogramme japonica, these were analyzed cladistically by maximum parsimony to gain insights into cheilanthoid phylogeny and generic circumscriptions, which have long stymied pteridologists. Our analysis yielded 4 equally most parsimonious trees of 1570 steps. Two of these trees varied only in the relative positions of Onychium and Pteris in the global outgroup. The other two varied only in the relative positions of Pellaea pringlei and P. rotundifolia in the ingroup. Results based on rbcL sequences are concordant with those of recent studies of Argyrochosma, Hemionitis, and Bommeria that utilized a broad suite of characters, suggesting that rbcL-based inferences in less meticulously studied cheilanthoid groups also convey meaningful information. Among the insights into cheilanthoid phylogeny and generic circumscriptions offered by rbcL sequences are the following. Llavea does not belong in subfamily Cheilanthoideae. Pellaea and Cheilanthes are polyphyletic. The recent removal of 21 species from Notholaena to Cheilanthes and the segregation of Argyrochosma are supported. The transfer of Hemionitis elegans to Bommeria is strongly supported, but the removal of the group of Doryopteris concolor to Cheilanthes is not. Trachypteris is sister to Doryopteris. The segregation of some small genera from Cheilanthes is supported, but these require further study through inclusion of additional taxa. Bommeria is the most basal ingroup element in this analysis.