A distinctive Dogtooth lichen, which is the only Peltigera with marginal soralia in Britain and Ireland. When sterile it may be confused with Nephroma parile, which lacks veins and has an almost smooth underside. Found in humid sheltered situations, on mossy trunks and rocks, usually in old woodlands. Very sensitive to acidifying air pollution and has declined in England and in Wales, but still has strong populations in the Highlands.
Thallus to 10–15 cm diam., usually less; lobes 1–1.5 (–3) cm broad, elongate (to ca 3 cm), radiating or ± randomly arranged (in old specimens), appressed for most of their length; margins ± raised, undulate, ± entirely sorediate; upper surface grey, blue-grey or rarely brown, smooth, ± shiny, occasionally somewhat scabrose, rarely pruinose towards the margins; soralia marginal, pale grey or slightly blue, rather coarsely granular and partly pigmented and partly corticate when young; lower surface with pale brown veins and ± simple rhizines. Apothecia rare, small, to 2 mm diam., rounded or ± elongate, eventually saddle-shaped, on short ascending lobes, dark brown or black. Ascospores 39–70 × 4–5 µm, 3 (-5)-septate. Thallus with tenuiorin, methyl gyrophorate, ± gyrophoric acid (C+ red), T1, T3 and additional unidentified terpenoids.
The only Peltigera with marginal soralia in Britain and Ireland. When sterile it may be confused with Nephroma parile, which lacks veins, has an almost smooth underside and a different chemistry.
On mossy trunks and rocks, often in sheltered situations, usually in old woodlands.
North and west Britain and western Ireland. Historically previously along the south cost and the North York Moors.
A suboceanic species in Europe, so extending far east in the Highlands, but avoiding drier areas, so apparently never present in much of the lowland England. Very sensitive to acidifying air pollution and now very rare or lost from the south coast and with very sparse and small surviving populations surviving in the rest of England and in Wales. Still with strong populations in the Highlands.
Britain: Notable species & International Responsibility species
Scotland: Priority Taxon for Biodiversity in Scotland
Wales: Near Threatened
Cannon, P., Magain, N., Sérusiaux, E., Yahr, R., Coppins, B., Sanderson, N. & Simkin, J. (2021). Peltigerales: Peltigeraceae, including the genera Crocodia, Lobaria, Lobarina, Nephroma, Peltigera, Pseudocyphellaria, Ricasolia, Solorina and Sticta. Revisions of British and Irish Lichens 20: 1-34.
Text by Neil A Sanderson based on Cannon et al (2021)