Acarospora cinerascens J. Steiner

in Arnold, Lich. Exs.: nr. 1500, 1890.
Synonyms: Acarospora alboatra H. Magn.
Distribution: N - TAA (Knudsen & al. 2015), VA (Piervittori & Isocrono 1999, Knudsen & al. 2015).
Description: Thallus crustose, episubstratic, areolate-subsquamulose, densely white-pruinose, the areoles 0.5-1(-2) mm wide, 0.3-0.6 mm thick, at first flat, then convex and fissured or reticulately grooved, dispersed or usually contiguous and separated by deep fissures, reddish brown, but almost always appearing white due to a thick layer of pruina, the margin most often dark. Epicortex to 30 µm thick, with small crystals dissolving in K; cortex 20-70 µm thick, brown in upper part, colourless in lower part, the cells mostly 3-4 µm wide; algal layer continuous, 100-150 µm thick; medulla white, to 0.4 µm thick, I-. Apothecia lecanorine, immersed, 0.3-1 mm across, with a black to brown-black sometimes slightly pruinose disc and a thick, often radially fissured thalline margin. Proper exciple prosoplectenchymatous, I-; epithecium brown; hymenium (80-)120-150 µm high, I+ blue rapidly turning red-brown, K/I+ blue; paraphyses 1-3 µm thick, the apical cells hardly swollen; hypothecium thin, colourless. Asci 100-200-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, 6-9(-12) x 2.5-3.5(-4) µm. Pycnidia immersed, dark. Conidia simple, ellipsoid, c. 2 x 1.5 µm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: on weathered base-rich siliceous rocks, restricted to dry-warm Alpine valleys with a continental climate. Superficially similar to A. versicolor, but a different species (Knudsen & al. 2015).
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Subcontinental: restricted to areas with a dry-subcontinental climate (e.g. dry Alpine valleys, parts of Mediterranean Italy)

Commonnes-rarity: (info)

Alpine belt: absent
Subalpine belt: very rare
Oromediterranean belt: absent
Montane belt: very rare
Submediterranean belt: extremely rare
Padanian area: absent
Humid submediterranean belt: absent
Humid mediterranean belt: absent
Dry mediterranean belt: absent

pH of the substrata:


Solar irradiation:








Altitudinal distribution:


Predictive model

From: Knudsen et al., Herziogia, 28, 2: 690-696, 2015 (Buschardt 420 - B) Scale: 0.5 mm