A very striking twig species with blood-red fruit on a steel grey thallus. Known from three 19th century English records. Not seen again until found in Hampshire in 2011 and 2012. Potentially recolonising from Europe after being lost to past air pollution, but may also be overlooked as Caloplaca cerina.
Thallus crustose, grey, moderately thick, of convex granules but smooth towards the margin, unevenly areolate towards the centre, often surrounded by a broad pale grey blue-tinged prothallus. Apothecia to 1 mm diam., contiguous, rounded to angular by mutual compression, constricted at the base; thalline margin grey, smooth and swollen at first, becoming thinner when old; disc brown-red, concave when young, becoming flat when mature; paraphyses unbranched or forked, septate, broadening towards the tips, the apical cells ca 3 µm diam. Ascospores 11–14 × 5–8 µm, ellipsoidal, septum 3–5 µm thick, about 1/4–1/2 of the length of the ascospore. Thallus K–, apothecial discs K+ purple.
A distinctive species, similar to Caloplaca cerina but differing in the brown-red rather than orange apothecial discs (Wetmore, 2007).
On smooth base-rich bark, especially twigs of fruit trees, Walnut and Poplars. Recently seen on White Poplar and Crab Apple twigs in a water meadow and grassy heathland respectively.
Rare, recently England (Hampshire), formerly known from S. Devon, Worcester and Cambridge. Possibly overlooked looked as Caloplaca cerina.
Appears very rare but may also be overlooked. Potentially recolonising from Europe after being lost to past air pollution.
Britain: Data Deficient
Cannon, P., Arup, U., Coppins, B., Aptroot, A., Sanderson, N., Simkin, J. & Yahr, R. (2024). Teloschistales, including Brigantiaea (Brigantiaeaceae), Megalospora (Megalosporaceae) and Amundsenia, Athallia, Blastenia, Calogaya, Caloplaca, Cerothallia, Coppinsiella, Flavoplaca, Gyalolechia, Haloplaca, Huneckia, Kuettlingeria, Leproplaca, Marchantiana, Olegblumea, Polycauliona, Pyrenodesmia, Rufoplaca, Rusavskia, Sanguineodiscus, Scythioria, Solitaria, Squamulea, Teloschistes, Variospora, Xanthocarpia, Xanthomendoza and Xanthoria (Teloschistaceae). Revisions of British and Irish Lichens 43: 1–75.
Wetmore, C.M. (2007b). Notes on Caloplaca cerina (Teloschistaceae) in North and Central America. Bryologist 110: 798–807.
Text by Neil A Sanderson based on Cannon et al (2024)