Chapsa subsorediata

This species is a bark-dwelling crustose lichen with a light gray-green thallus up to 5 cm (2 in) across and about 40–70 μm thick. The surface is smooth to uneven and is abundantly sorediate, with white, granular soralia about 0.2–0.5 mm wide. The photobiont is the green alga Trentepohlia. Calcium oxalate crystals are present in the photobiont layer and medulla, and the medulla is indistinct and white.^[2]

The fruiting bodies (apothecia) are angular to rounded, sunken in the thallus to partly protruding (immersed to erumpent), and about 0.5–1 mm in diameter. The disc is pale brown and heavily white-pruinose, and the margin is lobulate and also strongly white-pruinose; a columella is absent. Ascospores are produced eight per ascus and are ellipsoid, 5–9-septate, measuring 20–25 × 6–8 μm. No secondary metabolites were detected by thin-layer chromatography, and the thallus was unreactive to standard chemical spot tests (P–, K–).^[2]

The species is known from Peru (Madre de Dios), collected at the Los Amigos Research and Training Center (CICRA) in tropical lowland rainforest at about 270 m (890 ft) elevation. It was found growing on tree bark in secondary forest, with collections made in August 2008.^[2]