A very distinctive northern species of nutrient-enriched birds perch rocks in extreme coastal situations found in Outer Hebrides, Shetland Isles and St. Kilda. Forms pale yellow-green placodioid patches and has a C+ orange and UV+ bright orange thallus. Protoparmeliopsis muralis is distinguished by the broader and flattened, not convex, lobes and C– thallus.
Thallus to ca 5 cm diam., forming circular placodioid patches or rosettes, the margins of radiating convex lobes 3–6 × ca 1.5 mm, the centre becoming uneven and irregularly areolate, pale yellow-green, the centre darkest, surface smooth to slightly warted, not or sometimes white-pruinose. Apothecia 2–3 mm diam., sessile, eventually constricted at the base; thalline margin well-developed, swollen, striate to crenulate, flexuose or granular, scarcely exceeding the disc and sometimes excluded; disc flat to slightly concave, red-brown to dark brown, not or slightly pruinose; epithecium well-developed, yellow-brown, slightly granular; hymenium 80–90 µm tall; paraphyses 1.5–3 µm diam., unbranched or branched especially above, ± contorted, apices to 3–4 µm diam., irregularly thickened. Ascospores 8–12 (–14) × 4.5–6 (–6.5) µm. Thallus C+ orange, K–, Pd–, UV+ bright orange (arthothelin, thiophanic acid, 2,7-dichloronorlichexanthone, 1–3 other xanthones).
One of the few Myriolecis species with placodioid thalli. Protoparmeliopsis muralis is distinguished by the broader and flattened, not convex, lobes and C– thallus.
On nutrient-enriched rocks, especially the tops of boulders frequented by birds in extreme coastal situations.
Rare and local, Scotland (Outer Hebrides, Shetland Isles, St. Kilda).
A northern species at the southern edge of its range, so potentially threatened by climate change.
Britain: Near Threatened.
Scotland: Priority Taxon for Biodiversity in Scotland.
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).