Lecanora leptacina

Thallus of dispersed to aggregated, convex to subglobose squamules, the margins somewhat crenulate, tending to form an uneven areolate thallus with somewhat flattened and radiating margins, yellow to yellow-green; prothallus black. Apothecia (0.4–) 1–1.5 mm diam., at first immersed, becoming sessile but not or slightly constricted below; thalline margin persistent, well-developed, entire, becoming flexuose, crenate and bead-like with age; disc olivaceous to green-black or black, uneven to slightly convex, matt, often thinly white-blue pruinose; epithecium yellow-brown, with or without granules, K+ blue-green; hymenium 60–80 µm tall, yellow-brown above; paraphyses 1.5–2 µm diam., sparsely branched and anastomosed, apices to 4.5 µm diam., slightly thickened and brown. Ascospores (9–) 10–13 (–15) × (4.5–) 6–9 µm, ellipsoidal or narrowly ellipsoidal, walls ca 1 µm thick. Thallus C–, K–, Pd± yellowish, UV– (atranorin, psoromic and conpsoromic acids but see comments below).

Described as  distinctive member of the L. subfusca group in its broad sense by Cannon et al (2022), but a sequence from material from Alaska (Spribille et al, 2020) indicates it is actually in an isolated branch between the Lecanora polytropa group and the clade that includes Myriolecis, Protoparmeliopsis and Rhizoplaca. Spribille et al (2020) also question the chemistry given above; the type specimen contains usnic acid, isousnic acid and zeorin. Specimens from coastal Norway are concordant with the type specimen in lacking psoromic acid, but may contain small amounts of atranorin. The Scottish material needs checking, but the spot tests given are not those expected of a lichen with psoromic acid but do suggest the presence of atranorin. See also L. chlorophaeodes.