Systematic revision of species in Japan.

(Hydnaceae, Basidiomycota) exhibits endemic species diversity in East Asia; however, few comprehensive systematic studies have been conducted to date. Here, we performed morphological, ecological, phylogenetic, and biological evaluations of the taxonomy of species in Japan. In total, 186 Japanese specimens were used for morphological observations. Phylogenetic trees were constructed using sequence data of nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS) region and a portion of translation elongation factor 1-α (). Intra- and interspecific mating tests using 78 monokaryotic strains of 13 species did not conflict with species delimitation inferred from their ITS and phylogenetic relationships. This study provides detailed morphological descriptions of 15 rigorously identified species from Japan, nine of which are described as new: , and . Three species documented in this work are new to Japan: , and . The remaining three species (, and ), previously reported from Japan, are redescribed using data from newly collected materials. We also transferred two old species ( and ) from East Asian into other genera.