Polypodiaceae

Polypodiaceae is a family of ferns. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), the family includes around 65 genera and an estimated 1,650 species and is placed in the order Polypodiales, suborder Polypodiineae. A broader circumscription has also been used, in which the family includes other families kept separate in PPG I. Nearly all species are epiphytes, but some are terrestrial. Stems of Polypodiaceae range from erect to long-creeping. The fronds are entire, pinnatifid, or variously forked or pinnate. The petioles lack stipules. The scaly rhizomes are generally creeping in nature. Polypodiaceae species are found in wet climates, most commonly in rain forests. In temperate zones, most species tend to be epiphytic or epipetric. Notable examples of ferns in this family include the resurrection fern (Pleopeltis polypodioides) and the golden serpent fern (Phlebodium aureum). Two distinct circumscriptions of the family are in use. The Pteridophyte Phylogeny Group classification of 2016 (PPG I) uses a circumscription of Polypodiaceae in which the family is placed in the suborder Polypodiineae (eupolypods I), along with eight other families. The relationship between the families is shown in the consensus cladogram below. An alternative approach treats the suborder Polypodiineae as the family Polypodiaceae sensu lato, and reduces the families to subfamilies, so that the Polypodiaceae sensu stricto becomes the subfamily Polypodioideae. The broader circumscription is used by Plants of the World Online, as of August 2019; for example, the Dryopteridaceae, shown above as a separate family, is included in its Polypodiaceae. The broadly defined Polypodiaceae has been described as an 'unwieldy megafamily'. Molecular phylogenetic analysis has led to the division of the Polypodiaceae into six subfamilies, and to the inclusion of genera that have at various times been placed in other families, including the Drynariaceae, Grammitidaceae, Gymnogrammitidaceae, Loxogrammaceae, Platyceriaceae, and Pleurisoriopsidaceae. The following cladogram shows a possible phylogenetic relationship between the subfamilies based on an analysis published in 2008; at the time, Grammitidoideae was not separated from Polypodioideae. In the list that follows, the taxa shown with the '(=)' prefix are considered to be synonymyms for the accepted subfamily name that they follow. However, this does not necessarily imply that the subfamily contains all of the synonym's previous genera.