A revised classification of Dryopteridaceae based on plastome phylogenomics and morphological evidence, with the description of a new genus, Pseudarachniodes.

Abstract

Dryopteridaceae are the largest fern family and include nearly 20% of extant fern diversity, with 24 currently recognized genera. Recognition and delineation of genera within this family have varied greatly. The three-subfamily classification of Dryopteridaceae was based primarily on molecular phylogenetic relationships but lacked morphological evidence, and the phylogenetic relationships of the subfamilies and genera of Dryopteridaceae are only partially resolved. A comprehensive and robust phylogeny is urgently needed. The heterogeneous morphology of the current members of Dryopteridaceae makes the family and its subfamilies difficult to define by single morphological characteristics or even character combinations. We carried out phylogenetic analyses to reconstruct a highly supported phylogeny of Dryopteridaceae. Our analyses recovered 24 strongly supported clades grouped into seven major clades of Dryopteridaceae. Seven morphological characters including habit, rhizome shape, frond morphology, rachis-costae architecture, appendages on stipe base and lamina, and soral arrangement were found to be informative for identifying different major clades and clades in Dryopteridaceae. Based on phylogenetic reconstruction and morphological analysis, we presented an updated infra-familial classification of Dryopteridaceae with seven subfamilies and 24 genera including four newly proposed subfamilies (Ctenitidoideae, Lastreopsidoideae, Pleocnemioideae, and Polystichopsidoideae). Morphological character combinations of each subfamily are summarized, and a key is provided. Most genera sensu PPG I are recognized, with Stigmatopetris reclassified into Dryopteridoideae and Arthrobotrya considered a synonym of Teratophyllum. A new genus Pseudarachniodes is introduced. This revised classification will serve as a foundational framework for future investigations on taxonomy, biogeography, and diversification of the most species-rich Dryopteridaceae in ferns.