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 Cheilantho ideae). Together with GenBank sequences of an additional cheilanthoid and a 14-species outgroup comprising Pteridaceae, Vittariaceae, and Co niogramme japonica, these were analyzed cladistically by maximum parsi mony to gain insights into cheilanthoid phylogeny and generic circumsc riptions, which have long stymied pteridologists. Our analysis yielded 4 equally most parsimonious trees of 1570 steps. Two of these trees v aried only in the relative positions of Onychium and Pteris in the glo bal outgroup. The other two varied only in the relative positions of P ellaea pringlei and P. rotundifolia in the ingroup. Results based on r bcL sequences are concordant with those of recent studies of Argyrocho sma, Hemionitis, and Bommeria that utilized a broad suite of character s, suggesting that rbcl-based inferences in less meticulously studied cheilanthoid groups also convey meaningful information. Among the insi ghts into cheilanthoid phylogeny and generic circumscriptions offered by rbcL sequences are the following. Llavea does not belong in subfami ly Cheilanthoideae. Pellaea and Cheilanthes are polyphyletic. The rece nt removal of 21 species from Notholaena to Cheilanthes and the segreg ation of Argyrochosma are supported. The transfer of Hemionitis elegan s to Bommeria is strongly supported, but the removal of the group of D oryopteris concolor to Cheilanthes is not. Trachypteris is sister to D oryopteris. The segregation of some small genera from Cheilanthes is s upported, but these require further study through inclusion of additio nal taxa. Bommeria is the most basal ingroup element in this analysis.