Morphological and phylogenetic analyses reveal one new genus and six new species in Irpicaceae and Steccherinaceae (Polyporales, Basidiomycota) from the Yunnan-Guizhou Plateau, Asia.

Polyporales is a diverse group of Agaricomycetes that has received extensive attention and study. Species in Irpicaceae and Steccherinaceae (Polyporales) are important wood-decaying fungi that cause white rot on both angiosperm and gymnosperm wood. Recently, many studies have focused on the classification of Irpicaceae and Steccherinaceae, but the familial placements of some taxa remain unresolved. In the present study, phylogenies of species in the two families were reconstructed using multilocus DNA sequence data, including ITS, nLSU, mtSSU, tef1-α, and rpb2, as well as two combined datasets: ITS+nLSU+mtSSU+rpb2+tef1-α for Steccherinaceae and ITS+nLSU for Efibula and related species. Three new species of Efibula, one new species of Phanericium within the family Irpicaceae, and one new genus, Odentinium, including two new species, O. aurantium and O. cremeum, within the family Steccherinaceae, are described and illustrated. The genus Odentinium is characterized by resupinate basidiomata with an odontioid hymenial surface, a monomitic hyphal system with clamped generative hyphae, cylindrical cystidia that are strongly encrusted, and ellipsoid, smooth basidiospores. Furthermore, the evolutionary times of Polyporales, including Irpicaceae and Steccherinaceae, were inferred based on conserved regions of DNA sequences (ITS+nLSU+mtSSU+rpb2+tef1-α). Bayesian evolutionary analysis indicated that the ancestors of Irpicaceae and Steccherinaceae are estimated to have emerged with mean crown ages of 199.17 Mya and 142.95 Mya, respectively, followed by the genus Odentinium, with a mean crown age of 120.8 Mya.