Three new Stirtonia species (Arthoniales) from Reserva Muralha, NE Brazil, with a worldwide key to the species

Three new species are described in the small genus Stirtonia, all from NE Brazil, and all from one reserve of Caatinga forest in Paraiba. Stirtonia microspora is characterized by the small macrocephalic ascospores, S. nitida by the smooth thallus even covering the ascigerous areas and S. nivea by the pruinose, elongated ascigerous areas. This is an unexpected diversity of this mostly palaeotropical genus in the neotropics. A revised worldwide key to the known species is presented.