Tephromela follmannii

The thallus grows on rock and forms thick, pale patches divided into raised, warty areoles. It is whitish to cream-coloured and about 0.8–1.2 mm thick. It lacks both soredia (powdery propagules) and isidia (small outgrowths). Apothecia (fruiting bodies) are frequent and sit directly on the thallus. They are round, black, glossy, and typically up to 2 mm across, occasionally reaching 3 mm, with a persistent thalline rim around the disc.^[2]

Microscopically, the upper part of the apothecium is dark violet, and the hymenium is violet and stains blue in iodine (I+ blue), reaching about 150–200 μm in height; the true exciple is not apparent. The asci are Bacidia-type and 8-spored, and the ascospores are colourless and ellipsoid (about 10–11 × 6–7 μm). Reported lichen products include atranorin and a mixture dominated by alectoronic/β-alectoronic acids with minor collatolic acids; physodic and 4-O-methylphysodic acids were detected only in trace amounts.^[2]

Tephromela follmannii is known from basaltic rocks on four islands of the Canary archipelago: Tenerife, La Palma, Gran Canaria and La Gomera. It was described as ecologically flexible, but it seems to be most frequent at moderate to high elevations; collections span roughly 550–2,450 m.^[2]

On Tenerife it has been recorded in El Teide National Park around 1,900–2,050 m, in a montane shrub-dominated community locally referred to as "retamar". On La Palma it occurs from low-elevation ravines to high-mountain sites, including Canary pine forests and high-elevation shrublands ("codesar"). Records from Gran Canaria and La Gomera are also from basalt in pine-dominated habitats, including an old plantation on La Gomera at about 1,100–1,200 m elevation.^[2]