Galapagos Species Database

Thallus thin, continuous, forming a thin film encrusting bryophytes or plant debris; surface smooth and shiny, not pruinose; Apothecia sessile to ±stalked, lirellate; lirellae very broad and short, never branched (melaspileoid); labia thick, entire, black, typically soon covered by a thin thallus layer (see notes); disc concealed, a thin slit; exciple completely carbonized, carbonization extending below the hymenium; hymenium hyaline, clear (not inspers); ascospores hyaline, I+ bluish violet, 1(-2) per ascus, broadly fusiform, (80-)120-180 x 25-40 µm, muriform, 40-80 vs. 4-10 celled. Chemistry: No substances found; all spot tests negative.

The short, melaspileoid lirellae are most characteristic for this species, they are typically covered almost entirely by a thin thallus layer, that in parts may become eroded and then specimens may resemble Graphis plagiocarpa Fée, a similar species with short, prominent lirellae, known from continental South America, but not confirmed from the Galapagos. Graphis plagiocarpa typically has spores not longer than 120 µm and lirellae that are mostly blackened and only basally covered by the thallus. Although the spore size of Graphis cleistomma varies considerably within a specimen, the majority of mature spores is generally longer than 120 µm. Superficially very similar because of its short, lip-shaped lirellae is the newly described species G. pedunculata, a predominantly saxicolous taxon with distinctly stalked, blackened, melaspileoid lirellae that are only basally covered by the thallus. Unlike G. cleistomma, thalli of G. pedunculata contain norstictic acid, reacting K+ orange (red crystals), and its spores are transversally septate, not muriform.