A normally sterile lichen of warmer oceanic woods, that is easily overlooked as another C+ orange sorediate lichen with a yellowish thalli. It can be picked out from the common Pyrrhospora quernea and Lecanora expallens by the characteristic wide marginal band of corticate and warty thallus with pustulate soralia becoming confluent only in the centre of the thallus and the UV+ bright orange fluorescence. Found on acidic bark on older trees in undisturbed woodlands.
Thallus of dispersed to aggregated areoles, pale green- to brown-yellow, convex, margins entire, surface granular and composed of low warts or papillae; soredia arising on the surface of the areoles, initially from circular soralia but becoming confluent and spreading over the surface but usually leaving the margin of the thallus corticate, paler than the areoles, yellow-green to green-white; prothallus inconspicuous to black. Apothecia when present to 1.2 mm diam.; thalline margin becoming contorted and crenate to irregularly lobed; disc pale red-brown, shiny, not pruinose. Thallus C+ orange, K+ weakly yellow, Pd–, UV+ bright orange (atranorin, arthothelin, unidentified substances).
The common C+ orange sorediate lichens with yellowish thalli, Pyrrhospora quernea and Lecanora expallens, lack the characteristic wide marginal band of corticate and warty thallus laking soralia and have UV+ dull orange fluorescence. Loxospora elatina s. lat. (Sarrameanales, Sarrameanaceae) has a grey thallus with whitish soralia and a K+ immediately bright yellow reaction and soft soralia. Pertusaria flavida and P. flavocorallina are K– and have isidia rather than soralia. Thalli on rock closely resemble Pertusaria flavicans (Pertusariales, Pertusariaceae) which has larger soredia (to 100 µm diam.) and lacks atranorin.
On acidic bark on older trees (e.g. Oak, Beech, Sallow and Pine), usually in moist old woodlands, especially in sheltered poorly drained boggy sites. Rare or overlooked on acid and shaded rocks but also recorded on open granite outcrops near the coast in the south west. Most frequent in southern oceanic Atlantic woodlands, it also occurs in core rainforest areas as well, but is rarer here and typically found on south facing slopes.
Local. S. & W. Britain and Ireland. More frequent in the New Forest (Hampshire), the Dartmoor woods (Devon) and the Meirionnydd woods (N. Wales), but rather infrequently recorded beyond these areas.
A very localised species of larger oceanic woodlands, where it can be frequent in long undisturbed stands, however, it can colonise slowly into 19th Oak stands. Appears to require good light and some warmth, evident in its restriction to south facing slopes to the north. Potentially threatened by increasing shade in ungrazed woods.
Britain: Notable
Cannon, P., Malíček, J., Ivanovich, C., Printzen, C., Aptroot, A., Coppins, B., Sanderson, N., Simkin, J. & Yahr, R. (2022). Lecanorales: Lecanoraceae, including the genera Ameliella, Bryonora, Carbonea, Claurouxia, Clauzadeana, Glaucomaria, Japewia, Japewiella, Lecanora, Lecidella, Miriquidica, Myriolecis, Palicella, Protoparmeliopsis, Pyrrhospora and Traponora. Revisions of British and Irish Lichens 25: 1-83.
Text by Neil A Sanderson based on Cannon et al (2022)