New insights on the phylogeny of Tectaria (Tectariaceae), with special reference to Polydictyum as a distinct lineage

The fern genus Tectaria (Tectariaceae) Cav. is morphologically diverse and difficult in terms of recognizing species and species groups. To infer the systematic positions of some species and identity-unknown collections with special morphological characters, we undertook phylogenetic analyses based on sequences of five plastid regions (atpB, ndhF + ndhF-trnL, rbcL, rps16-matK + matK, and trnL-F). Three analysis methods (maximum parsimony, maximum likelihood, and Bayesian inference) were used to reconstruct the phylogeny of Tectaria. The most surprising result is that T. menyanthidis (C. Presl) Copel., T. ternata (Baker) Copel., and T. variabilis Tardieu & Ching are revealed to represent a distinct lineage from Tectaria, which should be called Polydictyum C. Presl, and is supported as sister to Pteridrys C. Chr. & Ching. Other accessions of Tectaria are well resolved into four major clades, which is consistent with the results of previous studies. Of the four clades, Clade II (T. subtriphylla (Hook. & Arn.) Copel. group) is unpredictable, with morphologically very diverse species clustered there, and is supposed to be a minor evolutionary line within Tectaria in the Old World. In addition, the position of the climbing genus Arthropteris J. Sm. and the utility of molecular data in recognizing species of Tectaria are briefly discussed. As a conclusion, we formally reinstate the genus Polydictyum by providing diagnostic characters, key to species, nomenclature, and information of detailed distribution and habitat for the currently known three species.