Ochrolechia xanthostoma


Ochrolechia xanthostoma

(Sommerf.) K. Schmitz & Lumbsch (1994)
Aspicilia poriniformis
Pertusaria trochiscea auct. brit.
Pertusaria xanthostoma
Conservation Status
LC NS (Key)
BLS Number
Taxon Photo
General Description

A distinctive and attractive lichen of open acid montane habitats, with fertile warts resembling a terricolous Pertusaria pertusa. Now confined to the Scottish Highlands, but with very old records from north west England and southern Ireland.  


Thallus thin, white to pale grey, very thin, areoles smooth or rimose-cracked, shiny (perhaps with an epinecral layer), eroding leaving a few flat to concave areoles between rock crystals; prothallus inconspicuous. Ascomata in warts, strongly resembling species of Pertusaria, 0.4–0.5 (–1.5) mm diam., irregularly semi-globose, constricted at the base, smooth, often crowded. Apothecia 1-3 (-6) per wart; visible as pink dot-like depressed poriform discs 50–100 μm diam., often surrounded by a thick shining pink to pale brown rim, with a thin thalline cuff below; epithecium red-brown, K– colourless. Asci 4-spored. Ascospores 55–75 (–85) × 30–40 μm, colourless, becoming brown when old, wall 1–1.5 μm thick, uniform, smooth. Thallus C–, K–, KC+ rose-pink, Pd–, UV+ brilliant white (alectoronic and α-collatolic acids). 

Distinguished by the globular fertile warts with several pinkish ‘ostioles’ closely resembling a species of Pertusaria. The only British specimen identified as Pertusaria trochiscea (from Scotland; Aberdeen, Peddie’s Hill), on mosses overgrowing serpentine, is incorrectly identified; it has been considered to be a race of O. xanthostoma lacking alectoronic acid (UV–, TLC).


On Calluna stems, siliceous rocks, old wall tops, mosses and soil, in fellfield habitat, usually above 700 m alt. but descending to sea level in the north. 

Distribution Map
Key to map date classes

C. and N. Scotland to the Orkney and Shetland Isles.

Threats & Status

Now confined to high quality acid montane habitats in the Scottish Highlands but with old records from north west England and southern Ireland.

Britain: Notable


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.

Text by Neil A Sanderson based on Cannon (2021)