Clitopilus reticulosporus, a new species with unique spore ornamentation, its phylogenetic affinities and implications on the spore evolution theory

Clitopilus reticulosporus (Entolomataceae, Agaricales) growing on rotting wood is described as a new species based on collections from Austria and Hungary. Multigene phylogenetic analysis of ITS, rpb2, LSU and mtSSU confirms the placement of C. reticulosporus in the Clitopilus-Rhodocybe clade in the Entolomataceae. It is nested within the subclade containing the species with clitopiloid spores (Clitopilus s. str.). Scanning electron microscopy studies demonstrate that the spores of this species have a peculiar reticulate ornamentation resembling an intermediate form between the clitopiloid type with longitudinal ribs, and the rhodocyboid type with irregular bumps and ridges. However, our ancestral character reconstruction suggests that (1) this character state is not an intermediate form and (2) the discovery of this new character state does not have a direct implication on the Entolomataceae spore evolution theory. Our phylogenetic reconstruction uncovered, at least, three distinct lineages in the Clitopilus s. str. clade, and suggest that sect. Clitopilus is monophyletic, while sect. Schyphoides and sect. Pleurotelloides are not.