Dryopteris (Dryopteridaceae) is one of the largest fern genera containing about 300 or more species. Sixty-five accessions representing all four subgenera and all 19 sections of Dryopteris recognized in current classifications, more than two-thirds of the species of Acrophorus, Diacalpe, Nothoperanema, and Peranema, three species of Arachniodes, three species of Cyrtomium, one species of Phanerophlebia, and two species of Polystichum, were sampled as ingroup in this study. Two species of Polystichopsis were used as outgroups. DNA sequences of five plastid loci (psbA-trnH spacer, rbcL gene, rps4-trnS spacer, trnL intron, trnL-F spacer) were used to infer the phylogeny of Dryopteris and related genera. Our study clearly demonstrated that the currently defined Dryopteris is paraphyletic in relation to a clade containing the monophyletic Acrophorus, Diacalpe, Nothoperanema, and Peranema. Peranema is resolved as sister to the remaining three genera, followed by Nothoperanema which in turn is sister to the Acrophorus+Diacalpe clade, but this relationship received low support. Three out of the four subgenera of Dryopteris recognized in current classifications are not recovered as monophyletic. Dryopteris subg. Nothoperanema, well supported as monophyletic by molecular and morphological data, is resurrected and re-circumscribed to contain species of the currently accepted genera Acrophorus, Diacalpe, Nothoperanema, and Peranema. Twenty-seven species are recognized and classified into four sections based on molecular and morphological evidence. Included in this treatment are 25 new combinations, names, species, and statuses, and neotypification or lectotypification of 14 names. The present study further located and cited types of an additional 28 related names, many of which have been unknown to science. Keys to sections and species and distributional information are given and nomenclatural issues are discussed. This paper also synonymized and excluded 33 nomenclaturally confusing names of Dryopteris that were formerly assigned to Acrophorus or Diacalpe.
