Redelimitation of Heteroradulum (Auriculariales, Basidiomycota) with H.australiense sp. nov.

Auriculariales accommodates species with diverse basidiomes and hymenophores. From morphological and phylogenetic perspectives, we perform a taxonomic study on Heteroradulum, a recently validated genus within the Auriculariales. The genus Grammatus is merged into Heteroradulum, and thus its generic type G.labyrinthinus is combined with Heteroradulum and G.semis is reaccepted as a member of Heteroradulum. Heteroradulumaustraliense is newly described on the basis of three Australian specimens. Heteroradulumyunnanense is excluded from this genus and its taxonomic position at the generic level is considered uncertain. Accordingly, the circumscription of Heteroradulum is re-delimited and the concept of this genus is adjusted by including irpicoid to poroid hymenophores and a hyphal system with clamp connections or simple septa. A key to all nine accepted species of Heteroradulum is presented.