An attractive crustose-squamulose lichen with blue-grey to brown appressed squamules set on an indigo-black hypothallus, usually with numerous apothecia with a red-brown disk and a soon excluded granular margin. A very local and threatened species of well lit base rich bark on veteran trees and found mainly in the eastern Highlands.
Thallus crustose, wide-spreading, of small closely appressed ± verrucose squamules 0.5–1 mm diam. on a thin but conspicuous indigo-black hypothallus; squamules scattered or contiguous-contorted, rounded or flattened or unevenly verrucose, pale grey, blue-grey, rarely olive-brown or brown, with a paler margin, slightly indented to irregularly crenulate, contiguous and overlapping or more often widely dispersed, appearing as a cracked-rimose crust. Apothecia 0.3–0.9 mm diam., often numerous, scattered or in clusters; disc bright red-brown to chestnut- brown, soon becoming markedly convex; thalline margin sometimes incomplete, grey, secondarily granular, soon excluded, often exposing a pale red-brown true exciple. Ascospores 10–14 × 8–9 μm, including the epispore 20–28 × 9–11 μm, colourless, ellipsoidal with one or rarely both ends attenuated. Lichen products not detected by TLC.
Characterised by the grey to olive, subcrustose thallus and the numerous small, very convex, often red-brown apothecia with a granular margin which is soon excluded. The squamules are sometimes widely dispersed, rounded with minute marginal lobes on a blue-black hypothallus.
On bark of old trees in waysides and wood edges, especially Fraxinus and Ulmus glabra, often in fissures and drier habitats than other Pannaria spp.
Very local, mainly in the eastern Highlands (especially in the Great Glen area), rare in the west Highlands and long lost from north west England.
A very localised species of sub-oceanic eastern Scotland, confined in well lit veteran tree in open pasture woodlands, wood edges and waysides. Vulnerable to over shading from dense regeneration from inappropriate grazing reductions in pasture woodland, safety fellings beside roads and Ash Dieback.
Britain: Vulnerable
Scotland: Priority Taxon for Biodiversity in Scotland
Cannon, P., Aptroot, A., Coppins, B., Sanderson, N. & Simkin, J. (2021). Peltigerales: Pannariaceae, including the genera Fuscopannaria, Leptogidium, Nevesia, Pannaria, Parmeliella, Pectenia, Protopannaria and Psoroma. Revisions of British and Irish Lichens 9: 1-16
Text by Neil A Sanderson based on Canon et al (2021)