Hypotrachyna altorum sp. nov., a new lichen from the cloud forests of Réunion Island, Indian Ocean

Hypotrachyna altorum (Ascomycota, Parmeliaceae) is described as a new corticolous lichen species from the montane cloud forests of Réunion Island (Mascarene archipelago). It is similar to the Brazilian species H. silvatica (Lynge) Hale from which it differs by the size and shape of the ascospores, medullary pigmentation, habitat and distribution. The new taxon is briefly compared to other Hypotrachyna species with similar secondary metabolites.