Bryoscyphus granulosus sp. nov., a “moss dieback” fungus on Campylopus with a sporodochium-forming morph

Bryoscyphus granulosus (Helotiaceae, Helotiales, Leotiomycetes, Ascomycota) is described from multiple western European collections on mosses in the genus Campylopus (Dicranales). The new species is unique among the currently described members of the genus in that it produces both sexual and asexual morphs comprising apothecia and sporodochia respectively. The sporodochium-forming asexual morph is commonly observed in the winter months, associated with distinctive necrotic “fairy rings” in populations of the European non-native moss, C. introflexus in a variety of habitats. However, sporodochia have also been collected on the European native host species, C. atrovirens, prompting questions on the origin of the fungus and its potential ecological impact on bryophyte communities. Here, the new species is fully described, supported by molecular data and culture characteristics. A preliminary phylogenetic analysis of Bryoscyphus is presented along with a worldwide key to the eleven currently known species of the genus. Finally, the ecological significance of B. granulosus as a natural biological control agent for C. introflexus is discussed.