FERN PHYLOGENY BASED ON RBCL NUCLEOTIDE-SEQUENCES

We analyzed nucleotide variation in rbcL (the gene encoding the large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase) from 99 ge nera of leptosporangiate ferns representing 31 of the 33 extant famili es. Phylogenetic relationships were inferred using three meth ods: nei ghbor joining, maximum parsimony, and maximum likelihood. All three me thods resulted in optimal trees that were similar. Within the context of those taxa examined, these trees suggest that: 1) Polypodiaceae, Gr ammitidaceae and Pleurosoriopsis form a monophyletic group that is mos t derived among indusiate ferns; 2) Davallia is closely related to the Polypodiaceae; 3) Tectoria is related to Oleandraceae rather than to other members of Dryopteridaceae; 4) Rumohra and Elaphoglossum are clo sely related; 5) Dryopteridaceae are polyphyletic; 6) a monophyletic g roup consists of Polypodiaceae, Grammitidaceae, Davalliaceae, Oleandra ceae, Nephrolepidaceae, Lomariopsidaceae, Dryopteridaceae, Thelypterid aceae, Blechnaceae, Aspleniaceae, and Pleurosoriopsis; 7) Dennstaedtia ceae, Monachosoraceae, Pteridaceae, Vittariaceae, and the previous cla de form a monophyletic group; 8) Dennstaedtiaceae are polyphyletic; 9) tree ferns in the Cyatheaceae, Metaxyaceae, and Dicksoniaceae form a monophyletic group that emerged early in the diversification of leptos porangiate ferns; 10) Plagiogyriaceae and Loxomataceae emerge with the tree ferns; 11) heterosporous water ferns form a monophyletic group t hat diverged prior to the tree ferns; 12) Schizaeaceae, Cheiropleuriac eae, Dipteridaceae, Gleicheniaceae, Matoniaceae, and Hymenophyllaceae are basal to the heterosporous aquatic ferns; and 13) Osmundaceae are the most basal lineage of the leptosporangiate ferns.