Basidioradulum mayi and B. tasmanicum spp. nov. (Hymenochaetales, Basidiomycota) from both sides of Bass Strait, Australia.

Basidioradulum was morphologically considered to be a synonym of Xylodon. Here, its independence within Hymenochaetales is confirmed from a phylogenetic perspective. Basidioradulum radula, the generic type, is widely distributed in Northern Hemisphere. Two Southern Hemisphere species close to B. radula are newly described as B. mayi and B. tasmanicum, respectively, from Victoria and Tasmania, Australia. Basidioradulum mayi differs from B. radula by lack of cystidia. Moreover, the hymenial surface of B. radula is normally much more strongly hydnoid than that of B. mayi. Basidioradulum tasmanicum is distinct from B. radula and B. mayi by having capitate cystidia, ellipsoid to subglobose basidiospores, and crystal-covered hyphae. Although morphologically distinct, the two new species isolated by Bass Strait have an almost identical ITS region, and could not be differentiated by nLSU- and ITS-based phylogenetic analyses. This case reminds us that basing phylogeny simply on the ITS as a barcode region may underestimate fungal species diversity.