Atla alpina is a species of saxicolous (rock-dwelling), crustose lichen in the family Verrucariaceae, and the type species of the genus Atla. Found in Europe, it was formally described as a new species in 2008 by Sanja Saviàand Leif Tibell. The type specimen was collected near Djupdalsvallen (MittÃÂ¥kläppen, Härjedalen, Sweden) at an altitude of , where it was found growing on northwest-facing, vertical slate rocks. In addition to Sweden, the lichen has been recorded from Scandinavia, Spitsbergen, Novaya Zemlya, Austria, and Germany, at elevations ranging from .
Atla alpina is a crustose lichen characterized by a thin thallus (the main body of the lichen) that forms minute measuring 0.4âÂÂ0.6 mm wide. These areoles have irregular, slightly uneven surfaces, ranging in colour from grey to dark greenish grey. The thallus sometimes appears minutely , thin, and matt, or it may be partly immersed in its substrate, emerging only as blackish green patches. The primary is an unidentified green alga, while small, almost black colonies of the cyanobacterium Nostoc are frequently found associated with the thallus, suggesting they may also participate in the symbiotic relationship.
The reproductive structures, , are relatively large (0.71âÂÂ0.87 mm in diameter), shiny black, and almost spherical. They are and broadly connected at the base without a thalline covering. The (outer protective layer) is thick, measuring approximately 80âÂÂ120 üm, with a strongly black outer layer. The (inner wall) is 15âÂÂ25 üm thick, brown, and composed of narrow, concentrically arranged cells that become paler in the lowermost part.
Mature asci lack apical thickening and measure 153âÂÂ178 üm by 70âÂÂ112 üm, containing eight spores each. The ascospores are large (70.1âÂÂ83.0 üm by 39.1âÂÂ49.0 üm), broadly ellipsoidal, and very dark brown when mature. They have a muriform structure with 7âÂÂ8 transverse walls and 3âÂÂ4 longitudinal walls in the central part. When treated with iodine, the gel stains red, and with potassium iodide, it turns blue.