Cora arborescens is a little-known species of basidiolichen in the family Hygrophoraceae. It was formally described as a new species in 2016 by Manuela Dal Forno, José Luis Chaves, and Robert Lücking. The specific epithet arborescens refers to its growth on trees. The lichen is only known from the type locality near Cerro de la Muerte in Costa Rica.
Cora arborescens is a basidiolichen in the family Hygrophoraceae (order Agaricales). It was described in 2016 by Manuela Dal Forno, José Luis Chaves, and Robert Lücking from material collected in a high-elevation cloud forest near Cerro de la Muerte, Costa Rica. The epithet, arborescens, refers to the lichen's epiphytic habit on tree branches and twigs. Although superficially similar to species such as C. canari, C. smaragdina, C. udebeceana, C. viliewoa, and C. boleslia, molecular analyses show that these taxa are not closely related.
The thallus of Cora arborescens is epiphytic and foliose, forming rosettes up to 5 cm across. It comprises two to five semicircular, somewhat overlapping () lobes, each 1.5âÂÂ4 cm wide and 2âÂÂ2.5 cm long with short radial sutures. When fresh the upper surface is emerald green, even, and , showing faint concentric colour zoning; margins are thin, rolled in (), and also glabrous. Dried material turns uniformly light grey. The lower surface lacks a (it is ) and presents a light-grey, felty-arachnoid medulla.
In section the thallus is 240âÂÂ330 micrometres (üm) thick. The upper cortex is viaduct-shaped: a 20âÂÂ25 üm layer of densely packed periclinal hyphae overlies a 40âÂÂ100 üm zone of anticlinal hyphae. The is 80âÂÂ155 üm thick and aeruginous green, while the medulla is 45âÂÂ90 üm thick and contains numerous hyphae 3âÂÂ6 üm wide; clamp connections are absent. The hymenophore forms diffuse, concentric, patches up to 0.5 mm long and 5 mm broad with a pale yellow-orange, smooth surface and slightly felty, involute margins. Sections (80âÂÂ115 üm thick) reveal plentiful palisade-like basidioles (15âÂÂ25 à4âÂÂ6 üm) and scattered four-spored basidia (20âÂÂ30 à4âÂÂ6 üm); basidiospores have not been observed. Thin-layer chromatography detected no secondary metabolites.
As of its original publication, the species was known to occur only in its type locality in TapantàNational Park, Cartago Province, Costa Rica, at 3,300âÂÂ3,400 m elevation. It grows epiphytically on tree branches and twigs in sub-Andean cloud forest conditions characterised by high humidity, frequent mists, and rapid wet-dry cycles. Cora arborescens is among the 18 Cora species found in Costa Rica and is one of 12 species in the genus for which Costa Rica is the type locality.