Phylogenetic Analyses of rdcL and Nuclear Ribosomal RNA Gene Sequences in Dennstaedtiaceae

Sixteen new sequences of the chloroplast gene rbcL were used to assess evolutionary relationships in Dennstaedtiaceae. Sequence data from nuclear 18S rRNA genes from several dennstaedtioid ferns were also analyzed and found to support some of the inferences based on rbcL data. Of the 1860 nucleotide sites of the 18S rRNA gene examined, 215 sites (11.6%) were variable and 71 sites (3.8%) were phylogenetically informative. The 18S rRNA gene appeared to be evolving at about one ninth of the rate of rbcL, and therefore 18S data should provide increased resolution for phylogenetic studies of the early branches in fern evolution. In the context of those species sampled, the following phylogeneticpatterns were evident from maximum parsimony and maximum likelihood analyses of rbcL: 1) Dennstaedtia was the only genus that was not monophyletic: Leptolepia and Microlepia diverged from within Dennstaedtia; 2) Tapeinidium did not emerge with the lindsaeoid genera, in which it is usually treated, but instead diverged at the base of the dryopteroid clade; 3) Lonchitis diverged at the base of the lindsaeoid clade, asin previous analyses of rbcL, a pattern supported by phylogenetic analysis of 18S rDNA; 4) Saccoloma emerged within the Hypolepis clade; 5)Orthiopteris (a segregate genus of Saccoloma) diverged after Dicksoniaceae but before all other clades of higher indusiate ferns; 6) Coptodipteris (usually treated as Dennstaedtia) emerged as a sister to Soccoloma; 7) Dennstaedtiaceae sensu late appear to be polyphyletic, with the lindsaeoid genera (plus Lonchitis) emerging as a separate clade to Dennstaedtiaceae sensu stricto; 8) Monachosorum diverged from within Dennstaedtiaceae sensu stricto