Ramalina arsenii sp. nov. belongs to the R. pollinaria group and is easily recognized by its ITS barcode and several micro-morphological characters that are diagnostic in a European context: small size, less than 3 cm long; soralia developing on the underside of lobe apices; absence of excavate depressions on the lower side. Its ecological niche (i.e. rock outcrops and especially underhangs of slightly calcareous rocks, at low and mid altitudes) is also unique. Ramalina arsenii is frequent and locally abundant in France (Alps, Cantal) and Switzerland (western Alps), and is also known from Germany and the Spanish side of the Pyrenees.
