Taxonomy of Pluteus eugraptus and morphologically similar taxa

Abstract

The status of the taxa morphologically similar to Pluteus eugraptus (Basidiomycota, Agaricales) was investigated with morphological and molecular (ITS region) characters. This group of species belongs in Pluteus sect. Celluloderma based on morphological and molecular characters. Two species, Pluteus multiformis, from Spain and Pluteus eludens from Madeira, Portugal, Russia and USA, are described as new. Both species share pigmented cheilocystidia and a pileipellis composed of both clavate-spheropedunculate and elongated elements with P. eugraptus, but they can be separated based on the characteristics of the cystidia and pileipellis. Pluteus multiformis is characterized by the scarce pleurocystidia, clavate cheilocystidia and caulocystidia and highly polymorphic elements of the pileipellis. Pluteus eludens is characterized mainly by utriform pleurocystidia. Pluteus eugraptus is known only with certainty from the type collection (Sri Lanka), which has been re-examined here, and it is characterized by narrowly lageniform pleurocystidia. Phylogenetic analyses based on ITS region sequence data supported the separation of P. multiformis, P. eludens and an additional collection from Japan that likely represents the true P. eugraptus.