Pluteus arizonicus, a new species from Western North America

A new species of Pluteus section Pluteus is described based on collections made in Arizona (USA). The new species is found in high-elevation, conifer dominated forests in the American Southwest, and it fruits directly on conifer wood or wood debris/conifer duff under Pinus, Picea, Pseudotsuga and/or Abies . Based on the phylogenetic analyses of ITS and translation elongation factor 1-alpha (tef1) sequences, P. arizonicus is closely related to P. brunneidiscus , but it differs in the smaller basidiospores, less distinct ornamentation on the pleurocystidia and habitat. Other close relatives ( P. kovalenkoi, P. shikae ) occur exclusively in Eurasia.