Rhizocarpon coeruleoalbum (Kremp.) Zahlbr.

Cat. Lich. Univ., 4: 331, 1927. Basionym: Rehmia coeruleoalba Kremp. - Denkschr. kgl. bayer. bot. Ges., 4, 2: 211, 1861.
Synonyms: Buellia coeruleoalba (Kremp.) Th. Fr.
Distribution: N - TAA (Nascimbene & al. 2022), Piem, VA (Piervittori & Isocrono 1999). C - Umb (Ravera & al. 2011).
Description: Thallus crustose, episubstratic, continuous to rimose-areolate, white to (bluish) grey-white, pruinose, forming patches to 5 cm in diam., rarely delimited by a black, but grey-pruinose prothallus. Areoles mainly angular, flat to slightly convex. Apothecia lecideine, black, 0.5-1.8 mm across, with a flat to weakly convex, epruinose or slightly pruinose disc, and a thick, persistent, usually pruinose proper margin. Proper exciple dark green-brown in outer part, pale brown to colourless within, containing K+ yellow crystals partly dissolving in K; epithecium olive-green, K+ intensifying green, with the same crystals as the exciple; hymenium colourless, 90-160 µm high; hypothecium dark brown, K-, without crystals. Asci 8-spored, clavate, fissitunicate, with a well-developed tholus, lacking an ocular chamber, Rhizocarpon-type. Ascospores 1-septate, hyaline or sometimes pale green when overmature, 13-20 x 5-10 µm, halonate. Photobiont chlorococcoid. Spot tests: medulla K+ yellow or rarely K+ yellow turning red, C-, KC-, P- or P+ orange. Chemistry: medulla with stictic acid, rarely with norstictic acid, or without lichen substances.
Note: on weakly calcareous or base-rich siliceous rocks, especially calcareous schists, with optimum above treeline.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

Commonnes-rarity: (info)

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

pH of the substrata:

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Solar irradiation:

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Aridity:

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Eutrophication:

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Poleotolerance:

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Altitudinal distribution:

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Predictive model
Herbarium samples

Einar Timdal - Source: http://nhm2.uio.no/lav/web/index.html - CC BY-NC