Gymnographopsis aptrootiana (Graphidales), a new addition to a poorly known genus with unique morphological features

The new species Gymnographopsis aptrootiana is described from tree bark in rain forests of Costa Rica and Guyana. It is placed in Gymnographopsis based on the combination of a partially ecorticate thallus, lirellate ascomata with partly exposed disc, and small, non-amyloid (I–), septate ascospores. Overall, it is most similar to G. koreaiensis, but differs in the 1-septate ascospores and the formation of disc-shaped schizidia, as well as its unusual chemistry with three unidentified compounds. We provide a modern overview of the genus Gymnographopsis, a key to the five currently accepted species, and a discussion of its position in Graphidaceae s.lat. We dedicate this work to our long-standing colleague, friend, and collaborator in the TICOLICHEN project, André Aptroot, for his invaluable contributions to tropical lichenology, on the occasion of his 65th birthday.