The beautiful fern species Didymochlaena truncatula (Sw.) J.Sm. is commonly grown as a houseplant, and is sometimes known as the mahogany maidenhair or mahogany fern (Fig. 1). Before the advent of molecular phylogenetics the mono-specific genus Didymochlaena Desv. (Desvaux, 1811) had often been included in the families Aspleniaceae, Dennstaedtiaceae, Dryopteridaceae, Polypodiaceae, or its own family. Shapes of sori and indusium are the most important characters for taxonomic studies of ferns. Didymochlaena has elliptic-oblong sori and indusium which can be distinguished from the related species. Recent molecular studies confirmed that it is a member of eupolypods I, but its familial placement has been controversial.

A recent study by Prof. ZHANG Libing and Dr. ZHANG Liang of Chengdu Institute of Biology (CIB) provided new insights into the placement of Didymochlaena. In the study, they performed phylogenetic analyses (MP, ML, BI) based on DNA data from five plastid loci (atpA, rbcL, rps4-trnS,trnL,trnL-F) of 88 accessions representing 79 species in 20 genera of all 9 families currently recognized in eupolypods I as ingroup and 5 species from 3 families of eupolypods II as outgroups. The reconstructed phylogeny s resolved Didymochlaena as sister to the rest of eupolypods I with strong support and deeply isolated from any other extant group of ferns (Fig. 2). This resolution is consistent with its sorus/indusium shape and a previous phylogenetic analysis based on both plastid and nuclear loci. Sorus shape, spore characters, and chromosome number previously used to place the genus in Dryopteridaceae are in fact not synapomorphies of the family. Their study clearly indicated that the family Didymochlaenaceae should be recognized. They validated the name as Didymochlaenaceae Ching ex Li Bing Zhang & Liang Zhang which was previously proposed by Ching.

This study entitled “Didymochlaenaceae: A new fern family of eupolypods I (Polypodiales)” has been published in Taxon 64 2015: 27–38.