Dendrographa austrosorediata

The lichen forms an indeterminate, crustose thallus that lies flat or develops shallow blister-like swellings which may curl slightly at the margins. Thalli are whitish-grey, very finely cracked (the rimose fissures intersect roughly every 0.1 mm) and only 0.1–0.2 mm thick. A thin black prothalline line may be visible at the colony edge. The cortex is 20–40 micrometres (μm) thick, the medulla is not differentiated, and the photobiont is of the green algal genus Trentepohlia, with cells 6–11 μm in diameter.^[2]

Vegetative propagation dominates: minute, whitish- to bluish-grey soredia (18–32 μm) arise in discrete convex soralia 0.2–0.4 mm across which later coalesce, ultimately covering much of the thallus surface. The side of each soralium that faces the light often darkens, producing an asymmetrical, blackened zone. Sexual and asexual fruit-bodies have not been observed, and no pycnidia are known.^[2]

Chemically, both thallus and soredia give a C+ (red) reaction; thin-layer chromatography detects erythrin and lecanoric acid.^[2]

Dendrographa austrosorediata colonises dry, overhanging faces of maritime granite in the upper supralittoral 'grey zone' of coastal cliffs, a microhabitat characterised by intermittent sea spray but protection from direct wave impact. At the type locality it occurs about 10 m above sea level, sharing the rock surface with other saxicolous Roccellaceae and a suite of cosmopolitan crustose lichens.^[2]

At the time of its original publication, the species was known only from the type locality in Santa Catarina, southern Brazil, where it appears to be endemic; no additional populations had been reported despite targeted surveys of nearby littoral habitats.^[2]