Taxonomic update of Clitocybula sensu lato with a new generic classification.

The taxonomy and phylogeny of the hydropoid clade (genera Clitocybula s.l., Megacollybia, Leucoinocybe gen. nov., Hydropus, Trogia, Gerronema, Porotheleum and Lignomphalia gen. nov.) in Europe is studied using morphological and molecular approaches; the first three genera in detail including all known European species. Only two European species remain in Clitocybula s.str., Clitocybula lacerata and Clitocybula familia. The European C. lacerata is a species complex which should be treated as C. lacerata agg. at the current state of knowledge. A neotype originating from type area was designated to fix the application of the name. The presence of American species Clitocybula abundans in Europe is insufficiently proved. "Clitocybula dryadicola ˮ belongs to the genus Hydropus, and Clitocybula tilieti has an unclear systematic position. The results showed that Megacollybia and Leucoinocybe represent independent genera separated from Clitocybula. The genus Leucoinocybe is validly published with two European species, Leucoinocybe lenta and Leucoinocybe taniae. "Clitocybula flavoaurantia" proved to be conspecific with the latter species. The genus Lignomphalia is published for "Pseudoomphalina lignicola", a lignicolous omphalinoid species. The Indian "Clitocybula sulcata" is transferred to Leucoinocybe and "Clitocybula atrialba" to Gerronema. The first European records of Megacollybia marginata are published.