Porina atlantica


Porina atlantica

(Erichsen) P.M. Jørg. (2000)
Porina guaranitica auct. brit. p.p.
Porina heterospora auct. brit.
Porina nucula auct. brit.
Porina rhodostoma auct. brit.
BLS Number
Taxon Photo
General Description

A very rare southern oceanic species in Ireland and Britain, where it is known from temperate rainforests in south west Ireland and a single ravine in North Wales. Mainly found on base rich bark on old Oaks but rarely also rock. An orange-brown isidiate species similar to Porina hibernica, Porina rosei and Coenogonium confusum. Porina atlantica differs from these species in the thicker and taller more branched isidia than these species, with a cortex which has numerous strongly projecting cells and the rough thallus surface with convex lumps.


Thallus superficial, pale brownish cream, often with lightly convex areas separated by furrows; isidia present, orange-brown, discrete or crowded, isodiametric when young, soon ± cylindrical, branched and coralloid, fragile, to 0.5 mm high, branches 50-80 μm diam., appearing papillose under the microscope, with a cortex which has numerous strongly projecting cells; perithecia frequent, mostly immersed (in Irish material) to prominent, apex light reddish brown; involucrellum containing numerous large crystals, orange(Porina-yellow); exciple yellow. Ascus apex rounded, without a ring structure. Ascospores 6- to 9 (-10)-septate, 56–66 × 11–14 μm.

Sterile material can be distinguished from P. hibernica by the larger branched isidia with a papillose surface and the convex lumpiness of the thallus surface. Porina rosei is more similar but has thinner isidia, with less projecting cortex cells and a smooth thallus.


On base-rich bark of Quercus, sometimes overgrowing bryophytes, rarely rock.

Distribution Map
Key to map date classes

Very rare. S.W. Ireland (N. Kerry, W. Cork, Limerick), N Wales (Merioneth).

Threats & Status

Not assessed in Britain but likely to be rare and very threatened.


Orange, A., Cannon, P., Malíček, J., Sanderson, N., Coppins, B. & Simkin, J. (2021). Ostropales: Porinaceae, including the genus Porina. Revisions of British and Irish Lichens 4: 1-12.

Text by N A Sanderson, based on Orange et al (2021)