Lepra leucosora
Description from Cannon et al (2021) below.
Forms circular colonies up to 10 cm diam.; thallus thick, pale to dark grey, cracked, areolate, with a zoned margin, prothallus absent; upper surface rough with warts 0.5– 1.5 mm diam.; circular white soralia abundant, crowded towards the centre of the thallus but remaining discrete; soredia coarsely granular. Thallus K–, KC–; medulla C–, K± dirty brown; soralia C–, K± dirty brown, Pd+ yellow changing to red, UV– (protocetraric acid).
Formerly regarded as synonymous with L. aspergilla but differs in chemistry, the warted upper surface and the neat, rounded soralia.
On slightly basic rock in coastal sites, including walls and churchyards, preferring slightly sheltered situations.
Rare. Channel Islands, across Europe including inland sites.
Cannon, P., Kukwa, M., Coppins, B., Fletcher, A., Sanderson, N. & Simkin, J. (2021). Pertusariales: Ochrolechiaceae, including the genera Lepra, Ochrolechia and Varicellaria. Revisions of British and Irish Lichens 5: 1-17. Link