Synonyms: Aspicilia montana (H. Magn.) Creveld; Lecanora bahusiensis H. Magn.; Lecanora isidiata (H. Magn.) H. Magn.; Lecanora simoënsis (Räsänen) Zahlbr.; Lecanora simoënsis var. isidiata H. Magn.; Lecanora variegatula H. Magn.
Distribution: N - Ven (Nascimbene 2003), TAA (Nascimbene 2004), VA (Favero-Longo & al. 2006, Isocrono & al. 2008, Favero-Longo & Piervittori 2009), Emil. C - Sar. S - Si.
Description: Thallus crustose, episubstratic, areolate, pale grey to grey, sorediate. Areoles angular, often finely subdivided into smaller units, bearing orbicular, well-delimited soralia-like clusters of coarsely granular to coralloid, dark grey isidioid outgrowths. Medulla white, I-. Apothecia rare, lecanorine-aspicilioid, 0.4-1 mm across, immersed in the thallus, with a concave to flat, black disc and a thin thalline rim. Epihecium olive-green, N+ emerald green; hymenium colourless; paraphyses simple or sparingly branched, anastomosing, moniliform in upper part; hypothecium colourless. Asci 8-spored, clavate, the thin outer coat K/I+ blue, the wall and apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, 15-22 x 8-12 µm. Photobiont chlorococcoid. Spot tests: thallus K+ yellow turning red (needle-like red crystals) or rarely K+ yellow, C-, KC-, P+ bright to golden yellow. Chemistry: norstictic acid and/or stictic acid.
Note: a mostly sterile species with areolate thallus reacting K+ red, described from Finland as sorediate; the populations from the Alps have dense clusters of isidia later breaking down into soredia-like propagules (fitting Lecanora simoënsis var. isidiata H. Magn.). It grows on siliceous boulders visited by birds and is widely distributed, at least in the eastern Alps. The record from Sicilia (see Nimis 1993: 105), if confirmed, would suggest that the species should be looked for more intensively along the Apennines, in areas with siliceous substrata.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by isidia, or isidia-like structures (e.g. schizidia)