Updated description of Atheniella (Mycenaceae, Agaricales), including three new species with brightly coloured pilei from Yunnan Province, southwest China

An updated description of the genus Atheniella, combining macro- and micromorphological characters that elaborate on the original generic characterisation, is presented. Atheniella is characterised by a brightly coloured pileus, all tissues inamyloid and pileipellis covered with simple to branched excrescences. Previously, nine Atheniella species were known globally, of which three species were accepted in China. Three newly-recognised species classified in the genus are here formally described from Yunnan Province: Atheniella flavidasp. nov., A. rutilasp. nov. and A. taoyaosp. nov. The new species are characterised by a yellow, orange, pink or red pileus, fusiform cheilocystidia and pleurocystidia, non-smooth pileipellis, stipitipellis smooth or with cylindrical ornamentation, caulocystidia fusiform or subglobose, if present and all tissues inamyloid. Morphological descriptions, photographs, line drawings and comparisons with closely-related taxa are presented for the new species. A phylogenetic analysis of sequence data for the rDNA internal transcribed spacer region and nuclear large ribosomal subunit (ITS + nLSU) supported that Atheniella is resolved as monophyletic and also supported the taxonomic recognition of the new species. A key to the 12 species of Atheniella is also provided.