A revised generic classification for the Rhodocybe-Clitopilus clade (Entolomataceae, Agaricales) including the description of a new genus, Clitocella gen. nov.

Abstract

Morphological and phylogenetic analyses in previous studies have led to conflicting hypotheses regarding the generic classification for the taxa within the Rhodocybe-Clitopilus clade of the Entolomataceae Kotl. & Pouzar (Agaricales, Basidiomycota). The majority of species in the Rhodocybe-Clitopilus clade are classified as either <italic>Clitopilus</italic> (Fr. ex Rabenh.) P. Kumm. (basidiospores ornamented with longitudinal ridges) or <italic>Rhodocybe</italic> Maire (undulate-pustulate basidiospore wall ornamentation). Recent phylogenetic analyses have revealed that taxa with basidiospores that are ornamented with pustules (<italic>Rhodocybe</italic>) do not form a monophyletic lineage. Here, the systematics of the Rhodocybe-Clitopilus clade are evaluated using a multi-locus phylogenetic analysis of three partial protein coding gene regions: (i) the mitochondrial ATPase subunit 6 (<italic>atp6</italic>), (ii) the nuclear RNA polymerase second largest subunit (<italic>rpb2</italic>) and (iii) the nuclear translation elongation factor subunit 1-&alpha; (<italic>tef1</italic>). The results of this analysis provide support for five internal clades: (i) a Clitopilus clade, (ii) a Clitocella clade, (iii) a Clitopilopsis clade, (iv) a Rhodocybe s. str. clade and (v) a Rhodophana clade. Based on these results, a revised classification recognizing five monophyletic clades is proposed and the morphological characters used to distinguish them are outlined. <italic>Clitopilopsis</italic> Maire and <italic>Rhodophana</italic> are resurrected, the boundaries of <italic>Rhodocybe</italic> are amended, and <italic>Clitocella</italic> is described as a new genus with <italic>Clitocella mundula</italic> designated as the type species.