Gyalolechia fulgens
Thallus 1-3 cm diam., orange-yellow to pale yellow or whitish, sometimes rosette-like but often irregular and fragmented, ± placodioid. Marginal lobes neat, clearly differentiated, longer than broad, mostly over 1 mm wide, remaining ± discrete or often overlapping especially towards the centre, which often becomes verrucose-bullate with age, ± coarsely pale pruinose. Schizidia variably developed; in most populations part of the thallus surface is given over to their production which when shed, exposes the white medulla. Photobiont chlorococcoid.
Anamorph: not known.
Teleomorph: ascomata apothecia, often present, 0.5-1.5 mm diam., erumpent through the upper thallus layers, at first concave with an irregular thalline exciple, becoming flat or shallowly convex with a ± excluded margin, deep orange to yellow, contrasting with the paler thallus. Asci clavate, the upper part with a thickened wall and a strongly blueing outer layer, 8-spored. Ascospores 9-12 × 3.5-5 μm, 0(-1)-septate, ellipsoidal, pyriform or clavate, not polarilocular, hyaline.
Chemistry: thallus K+ purple (parietin and its precursor emodin), UV± dull pale orange (fragilin, caloploicin), apothecia K+ purple (physcion).
Assessed as Endangered (EN B1 & 2 ab (iii)) by Woods & Coppins (2012). The species is now extinct at four of its 16 historical sites.
According to Woods & Coppins (2012), most sites, although having statutory protection, are highly vulnerable to combinations of effects that may lead to an increase in taller vegetation (e.g. reduction in grazing, especially by rabbits, mild winters and lack of recent summer droughts, and nutrification) or excessive disturbance (e.g. over-grazing by livestock, recreational damage).
Now restricted to SW England (VC1 W Cornwall, VC2 E Cornwall, VC4 N Devon, VC6 N Somerset) and the Channel Is, with small populations in VC10 Isle of Wight and VC45 Pembrokeshire. It was formerly present in Suffolk and Sussex.
Colonizing bare ground or low moss mats in coastal dunes or grassland, more rarely soil-filled pockets on low limestone outcrops.