Variospora thallincola

Variospora thallincola is a species of saxicolous (rock-dwelling), crustose lichen in the family Teloschistaceae.

Taxonomy
It was formally described as a new species in 1875 by the botanist Hugh Algernon Weddell, who named it Lecanora murorum var. thallincola. Gustaf Einar Du Rietz raised it to species status in 1925, as Caloplaca thallincola. Ulf Arup and colleagues transferred the taxon to the genus Variospora in 2013, following a molecular phylogenetics-based restructuring of the family Teloschistaceae.

Description
Variospora thallincola is characterised by its, bright orange thallus that forms closely appressed, circular structures resembling cartwheels, each measuring 3–4 cm in diameter. The thallus features convex, finger-like ends, around 0.3–0.7 mm broad, which lie closely together and are separated by frequently parallel furrows. The central area of the thallus is convex and, and lacks , a powdery or waxy coating.

The species develops apothecia, the fruiting structures, which can be up to 0.8 mm in diameter and are generally scattered across the central area of the thallus. The of the apothecia is orange and becomes excluded as they age. The of these apothecia are brown-orange in colour and transform from flat to convex over time. Within the apothecia, the paraphyses (sterile filamentous structures) are loose, with some being while most fork towards their tips, which are slightly swollen. The of Variospora thallincola are distinctive for their swollen, lemon-shaped appearance, measuring 11–14 by 8–11 μm with a septum width of 4–5 μm, accounting for half the length of the ascospore. Both the thallus and the apothecia react to a potassium hydroxide (K) spot test by turning purple.

Habitat and distribution
Found on rocky coasts with siliceous stone, Variospora thallincola typically grows in the mesic to submesic-supralittoral zones. It prefers north-facing rock surfaces that are shaded. The lichen is widely distributed, having been reported from Africa, Asia, Europe, and North America.