rbcL data reveal two monophyletic groups of filmy ferns (Filicopsida : Hymenophyllaceae)

The "filmy fern" family, Hymenophyllaceae. is traditionally partitioned int o two principal genera, Trichomanes s.l. (sensu lato) and Hymenophyllum s.l ., based upon sorus shape characters. This basic split in the family has be en widely debated this past century and hence was evaluated here by using r bcL nucleotide sequence data in a phylogenetic study of 26 filmy ferns and nine outgroup taxa. Our results confirm the monophyly of the family and pro vide robust support for two monophyletic groups th;lt correspond to the tw classical genera. In addition, we show that some taxa of uncertain affinity , such as the monotypic genera Cardiomanes and Serpyllopsis, and at least o ne species of Microtrichomanes, are convincingly included within Hymenophyl lum s.l. the tubular- or conical-based sorus that typifies Trichomanes s.l, and Cardiomanes, the most basal member of Hymenophyllum s.l. is a plesiomo rphic character state for the family. Tubular-based sori occurring in other members of Hymenophyllum s.l. are most likely derived independently and mo re than one time. While rbcL data are able to provide a well-supported phyl ogenetic estimate within Trichomanes s.l.. they are inadequate for resolvin g relationships within Hymenophyllum s.l.. which will require data from add itional sources. This disparity in resolution reflects differential rates o f evolution for rbcL within Hymenophyllaceae.