Overview of the European species of the genus Clitocella (Entolomataceae, Agaricales) with notes on extralimital taxa

A revision, based on morphological and multigene analysis, of the Clitocella species currently present in Europe is provided. Portions of nrITS rDNA, nr28S rDNA (LSU), RNA polymerase II second largest subunit (RPB2), translation elongation factor 1-alpha (EF-1α), and ATPase subunit 6 (ATP6), were used to sort out the relationships of the species within the genus. Three subgenera were recognized: Clitocella subg. Clitocella encompassing C.popinalis, C.colorata, C.mundula, C.nigrescens, C.obscura and the new species C.solaris from Switzerland; the new Clitocella subg. Paraclitopilus including C.fallax and C.blancii; and the new Clitocella subg. Rhodopleurella for accommodating C. termitophila, a peculiar entity characterized by a pleurotoid habit and growing on decaying, abandoned termite nests in the Dominican Republic. Clitocella colorata originally described from China is here reported and described for the first time in Europe (Italy and Estonia). Rhodocybe cupressicola and Clitopilus ammophilus are reduced to later synonyms of Rhodopaxillus nigrescens; similarly, Clitopilus amarus is treated as a later synonym of Omphalia fallax while Rhodocybe amarella and R. ochraceopallida of Rhodopaxillus blancii. Finally, Austrian and Swedish herbarium collections identified as Rhodocybe, a doubtful taxon considered by several modern authors occasionally as either a similar but distinct species from R.popinalis or as a dwarfish, puny and odourless form of R. popinalis, have been proved to be R. tugrulii, a species recently described from Turkey and Estonia, and also later reported from Italy and USA.