The genus Dermoloma is more diverse than expected and forms a monophyletic lineage in the Tricholomataceae

We present the first phylogenetic evaluation of the genus Dermoloma, which is resolved as monophyletic and closely related to Pseudotricholoma, a poorly known Dermoloma-like lineage within the family Tricholomataceae. The position of Dermoloma is confirmed by the placement of the type species, Dermoloma cuneifolium, represented by multiple samples including the neotype. Based on our phylogenetic analyses, we recognised 25 European operational taxonomic units (OTUs) but could only assign species names to ten of them based on ex-type sequences. Furthermore, only five additional published Dermoloma names of uncertain status are available for the remaining 16 potential European species, thus demonstrating an unexpected amount of taxonomic diversity. Samples from Europe and North America seem to be endemic on a continental scale. North American samples formed six unique OTUs, but only one could be reliably named, Dermoloma hymenocephalum. Dermoloma is morphologically defined by basidiomata with brown, grey and white colours with a farinaceous odour and a pluristratous hymeniderm type of pileipellis. Our phylogenetic analyses support the subdivision of the genus into two subgenera and four sections, and species with inamyloid basidiospores are placed in subg. Dermoloma and those with amyloid basidiospores in subg. Amylospora. Both subgenera are further divided into two sections. The analysis of spore morphology shows that sect. Conica of subg. Dermoloma and sect. Nigrescentia of subg. Amylospora have a very distinctive spore shape. Sect. Atrobrunnea of subg. Amylospora showed relatively high variability of spores among species, but spores of sect. Dermoloma were similar and not useful for species discrimination.