Recent studies utilizing nucleotide sequence data have indicated that Grammitidaceae and Polypodiaceae form a monophylum, in which the monophyletic Grammitidaceae are nested in a paraphyletic Polypodiaceae. This hypothesis is tested with an enlarged rbcL data set and a new morphological data set. Nearly all proposed genera of Grammitidaceae and Polypodiaceae are included with one or more representatives in both data sets. The two data sets utilize the same taxa and are analyzed both separately and combined. Our analyses reveal monophyletic groups within both families (and the relationships among Grammitidaceae and Polypodiaceae). Several disputed genera in both families are shown to be polyphyletic or paraphyletic, e.g. Grammitis, Microgramma, Microsorum, and Polypodium, but many monophyletic units correspond with previously proposed genera, e.g. Campyloneurum, Pecluma, and Prosaptia. Several large clades have biogeographical continuity, being restricted to either the Paleotropics or Neotropics. The entire group probably had an Old World origin, whereas Grammitidaceae are sister to New World Polypodiaceae. However a number of genera have attained pantropical distribution, presumably in their relatively short history. Important changes in the classification are outlined. The phylogenetic results are compared with traditional taxonomic units based on morphological characters, and conflicts are discussed. Both families are primarily tropical/subtropical epiphytes, and some morphological characters may reflect adaptation to similar habitats. Such similarities cause conflicts in the recognition of natural groups with traditional and phylogenetic methods. The rbcL data set is used to recognize convergent characters and evolutionary trends in epiphytic plants.

Key words: biogeography, epiphytes, ferns, Grammitidaceae, phylogeny, Polypodiaceae