Two species of the Entoloma quadratum–murrayi complex from Japan, E. kermesinum sp. nov. and E. flavescens sp. nov.

We describe two new species, Entoloma. kermesinum sp. nov. and E.
flavescens sp. nov., which are confused with E. quadratum and E. murrayi,
respectively. We sequenced the large subunit of mitochondrial ribosomal
RNA, the nuclear ribosomal internal transcribed spacer region and 22
single-copy genes for 51 specimens of E. kermesinum, E. flavescens, E.
album, and related species. Species boundaries were assessed using the
molecular phylogenetics and population genetics approaches. Specimens of
E. kermesinum, E. flavescens, and E. album formed independent clades,
which were phylogenetically distinct from the specimens of E. quadratum
and E. murrayi collected around the type locality (i.e., New England).
Although the phylogenetic distance between E. flavescens and E. album was
small, gene flow between them was restricted in areas where they
coexisted, suggesting reproductive isolation. Therefore, these five
species can be treated as independent species. We found characteristics
useful for identifying E. kermesinum and E. flavescens. In particular, E.
kermesinum is characterized by a crimson to brown-red and fibrillose
pileus, finely covered by whitish fibrous scales; E. flavescens is
characterized by a lemon-yellow to tan and shiny-to-silky pileus. In
addition, relatively large basidiospores and clamp connections are
diagnostic features of these two species.