Distribution: N - Frl, TAA (Nascimbene & al. 2014, Nascimbene 2014, Nascimbene & Marini 2015), Emil (Fariselli & al. 2020). C - Sar (Zedda 2002, 2002b, Malíček & al. 2017). S - Cal (Puntillo 1996).
Description: Thallus crustose, episubstratic, smooth to warted, grey, whitish grey or yellowish white, sorediate. Soralia maculiform, orbicular, 0.3-0.6(-1) mm across, rarely confluent, concave or flat when young, later convex, when young sometimes delimited by a thin basal thalline rim; soredia finely granulose, 40-60 µm thick, pale grey to more often pale yellow. Apothecia rare, lecanorine, sessile or slightly constricted at base, 0.5-1.2 mm across. with a reddish brown, shiny disc, and a smooth, often sorediate thalline margin. Thalline exciple distinctly corticate, the cortex basally thickened, with abundant, small crystals insoluble in K; epithecium yellow-brown, with pigment not dissolving in K, without crystals; hymenium colourless, 50-80 µm high; hypothecium colourless to pale yellow, 20-45 µm high. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, (10–)12-15 x (5.5–)8-10 µm, the wall <1 µm thick. Photobiont chlorococcoid. Spot tests: thallus and margin of apothecia K+ yellow, C-, KC-, P+ yellow. Chemistry: atranorin (major), chloratranorin, zeorin, an unknown terpenoid (minor or accessory), and sometimes traces of fatty acids.
Note: a temperate species found on base-rich bark, especially on isolated Fraxinus in humid riparian woodlands. According to Malícek (in litt.), who examined the original material, the record of L. farinaria Borrer from Sardegna by Zedda (2002, 2002b), actually refers to this species, which is included in the Italian red list of epiphytic lichens as “Vulnerable” (Nascimbene & al. 2013c). See also note on L. allophana f. sorediata.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)