A world key to Stirtonia (Arthoniaceae), with three new Stirtonia species and one new Crypthonia species from the Neotropics

Abstract

A world key to the 21 species of Stirtonia is presented. Three new Stirtonia species are described from the Neotropics: Stirtonia ibirapuitensis Aptroot, Käffer & S. M. Martins, with whitish to cream amoeboid ascigerous areas with lichexanthone on a greenish thallus without lichexanthone and ascospores of 27–32×9·5–12·5 µm; Stirtonia punctiformis Aptroot & Sipman, with ascigerous structures of thallus colour, consisting of one or more brown asci with brown walls with surrounding tissue, in groups or irregular lines and brown ascospores 61–73×27–35 µm; and Stirtonia viridis Aptroot, L. I. Ferraro, Sipman & M. Cáceres, with ascigerous structures mostly linear, branched and anastomosing, whitish, and contrasting with the often greenish thallus and with ascospores 50–58×15–22 µm. In addition, a specimen of S. neotropica is reported that contains some patches of lichexanthone, S. curvata is reported new to the Neotropics from Brazil and the Netherlands Antilles, and S. nivea is reported new to the Northern Hemisphere from Puerto Rico. Also, Crypthonia divaricatica Aptroot & Sipman, with an irregular, thick thallus with divaricatic and usnic acids and flat white ascigerous areas and macrocephalic 5–9-septate ascospores 20–27×9·5–12·5 µm is described from Mexico. While only one Stirtonia species was known from the Neotropics as recently as 2009, the total number of Stirtonia species known from the Neotropics is now 12, an equal number to the 12 species that are known from the Palaeotropics.