Taxonomy, phylogeny and divergence times of Polyporus (Basidiomycota) and related genera

Polyporus is a taxonomically controversial genus which includes species belonging to six infrageneric groups. Recently, many species of Polyporus have been transferred into other related genera viz. Cerioporus, Favolus, Lentinus, Neofavolus and Picipes based on the phylogenetic and morphological analyses. To ascertain the relationships of Polyporus and its allied genera, eight DNA fragments viz. the internal transcribed spacers 1 and 2 with the 5.8S rDNA (ITS), the nuclear ribosomal large subunit (nLSU), partial translation elongation factor 1- gene (EF1-), the mitochondrial small-subunit (mtSSU), the -tubulin gene (TUB), the gene for RNA polymerase II largest subunit (RPB1), the gene for RNA polymerase II second largest subunit (RPB2) and the nuclear ribosomal small subunit (nSSU), are used in the molecular systematic studies. Phylogenetic analyses were carried out based on two combined datasets (ITS+nLSU) and (ITS+nLSU+EF1-+mtSSU+RPB1+RPB2+nSSU+TUB), and the results indicated that species of Polyporus and its related genera fell into six well supported clades: the picipes clade, the favolus calde, the neofavolus clade, the lentinus clade, the core polyporus clade and the squamosus clade. Moreover, the conserved regions of six DNA fragments (5.8S, nLSU, EF1-, RPB1, RPB2 and nSSU) were used to analyze the divergence times and evolutionary relationships of Polyporus and its related genera by using BEAST v1.8. Bayesian evolutionary analysis revealed that the ancestor of Polyporales split at about 141.81 Mya, while the mean stem ages of the six major clades of Polyporus and its allied genera were 49-63 Mya. Based on the combined analyses of morphology, phylogenies and divergence times, species in the picipes clade formed the genus Picipes by the coriaceous (fresh) to hard (dry) basidiomata and strongly branched skeleto-binding hyphae; species nested in the favolus clade and the neofavolus clade were separately treated as two distinct genera Favolus and Neofavolus; the polyporoid species in the lentinus clade with central and light-colored stipe and inflated hyphae were transferred into Lentinus, and the core polyporus clade was treated as Polyporus s. str. The squamosus clade contained species belonging to several different genera viz.