Tremella mayrhoferi, a new lichenicolous species on Lecanora allophana

Tremella mayrhoferi, inducing galls on the hymenium of Lecanora allophana, is described. The description is based on molecular, morphological and ecological data of 27 specimens from Finland, Norway, Spain, Sweden, and USA. The new species is easily distinguished from other lichenicolous Tremella species by its characteristic basidia with cells that elongate before the formation of epibasidia, combined with the macromorphology and host selection. Molecular phylogeny suggests that it forms a group with other species growing on Lecanora s. lat. and Lecidea s. lat., which is related to the Tremella species growing on Parmeliaceae, but not to Tremella s. str.