Acarospora subrufula
Thallus crustose, areolate; areoles 0.3-2 mm wide, rounded or irregular, markedly contiguous, often in lines following minor fissures in pale striate, pale to deep red-brown. Photobiont chlorococcoid.
Anamorph: not known.
Teleomorph: ascomata apothecia, numerous, round, mostly 1 (-3) per areole, aggregated, dark grey- to red-brown, darker than the thallus and often extending across the entire areole. Thalline margin somewhat prominent, very swollen and globular, white-striate, paler than the disc. Disc 0.1-0.3 mm diam., plane and sunken, oblong or kidney-shaped, rarely contorted, deep red chestnut brown. Hymenium 80-100 μm high. Interascal tissue of mostly unbranched paraphyses 100-110 µm in length, 1.5-2 μm diam. at the base, 2-4 μm diam. at the dark brown capitate apices, immersed in gel with a pale yellow epithecium. Asci clavate, multispored, the apical dome not staining in iodine. Ascospores 4-6 × 1-2.5 μm, ellipsoidal, hyaline, aseptate, without a gelatinous sheath or appendages.
Chemistry: thallus C–, K+ red, KC+ red (crystals), Pd+ yellow-orange (norstictic acid). The reactions are only clearly visible on the apothecium margin.
BLS species page - here.
Lichens Marins, Maritimes et Oceaniques - images here. Association Francaise de Lichénologie - images here.
Assessed as Vulnerable (D2) by Woods & Coppins (2012) due to its very restricted UK distribution. It is a BAP Priority Species and listed in Section 41 of the NERC Act 2006. Reported as declining in population in the years up to 2010 and not seen since 1982 except in the Channel Isles.
An inconspicuous species of rock crevices with areoles frequently obscured by the apothecia. These have thick swollen and often striate margins, that are usualy paler than the disc.
In GB&I, restricted to seven sites on the Scilly Isles (Tresco, St Mary's and Bryher), and the Land's End area of Cornwall (VC1). Apparently quite widely distributed in suitable maritime habitats in the Channel Isles.
Found on sunny, exposed, crystalline coastal granite rocks, especially in fissures.