Lecanora albula (Nyl.) Hue

Bull. Soc. bot. Fr., 44 (sess. extr.): 291, 1900 (1897).. Basionym: Squamaria albula Nyl. - Acta Soc. Sci. Fenn., 7, 2: 396, 1863.
Description: Thallus crustose, episubstratic, closely adnate, grey-green to yellowish green, but appearing white due to a dense pruina, usually forming irregular rosettes, the central parts irregularly areolate. Cortex poorly differentiated from the medulla, both inspersed with grey crystals. Apothecia abundant and crowded, lecanorine, (0.5-)1-1.5(-2.5) mm across, sessile, with a flat to slightly convex, pale brown to ochraceous disc, and a 0.05-0.15 mm thick, persistent, hardly raised, concolorous to yellowish green thalline margin. Thalline exciple K-; proper exciple colourless, K+ yellow; epithecium colourless to pale brownish green, with granular crystals dissolving in K; hymenium colourless to pale yellow, 60-70 µm high; paraphyses sparingly branched and anastomosing, 1.2-2 µm thick in lower part, slightly thickened at apex; hypothecium colourless or pale yellowish brown, K+ yellow. Asci 8-spored, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid to broadly ellipsoid, (7.5)8-11(-12.5) x (5-)5.5-7(-7.5) μm, thin-walled. Pycnidia immersed, with a pale yellow-brown ostiole, Conidia acicular to arcuate, up to 22 µm long. Photobiont chlorococcoid. Spot tests: thallus and thalline margin of apothecia K- or K+ indistinctly yellow, C-, KC+ yellow, P-. Chemistry: usnic acid, zeorin, a blue fatty acid, terpenoids.
Note: a species based on a type from the French Alps (Dauphiné), characterised by a relatively thick, whitish thallus with subeffigurate margins and apothecia of the L. polytropa-type, perhaps heterogenous in its current circumscription; on very sunny surfaces of rocks which are very poor in calcium, in warm-dry situations. Known from several localities throughout the Alps, but outside the Italian territory; to be looked for in the Italian Alps.
Growth form: Crustose
Substrata: rocks
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual

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Predictive model
Herbarium samples

M. Bertrand - Source: Roux C., Bertrand M., Poumarat S., Uriac P. 2022. Quelques espèces nouvelles saxicoles – calcifuges de Lecanora du groupe polytropa (Ascomycota, Lecanoraceae) découvertes en France. Bull. Soc. linn. Provence, 73: 79-120.

Jiří Malíček, Source: J. Malíček, H. Mayrhofer 2014. Herzogia 30(2):431-444

P.L. Nimis CC BY-SA 4.0
Herb. Cl.Roux (1563)

P.L. Nimis; Owner: Department of Life Sciences, University of Trieste
Herbarium: Herb. Cl.Roux (1563)