Additions to the taxonomy of Lagarobasidium and Xylodon (Hymenochaetales, Basidiomycota)

Lagarobasidium is a small genus of wood-decaying basidiomycetes in the order Hymenochaetales. Molecular phylogenetic analyses have either supported Lagarobasidium as a distinct taxon or indicated that it should be subsumed under Xylodon, a genus that covers the majority of species formerly placed in Hyphodontia. We used sequences from the ITS and nuclear LSU regions to infer the phylogenetic position of the type species L. detriticum. Analyses confirm Lagarobasidium as a synonym of Xylodon. Molecular and morphological information show that the traditional concept of L. detriticum covers at least two species, Xylodon detriticus from Europe and X. pruinosus with known distribution in Europe and North America. Three species currently placed in Lagarobasidium are transferred to Xylodon, viz. X. magnificus, X. pumilius and X. rickii. Three new Xylodon species are described and illustrated, X. ussuriensis and X. crystalliger from East Asia and X. attenuatus from the Pacific Northwest America. The identity of X. nongravis, described from Sri Lanka, is discussed.