Cladonia norvegica
A difficult to spot small Cladonia of humid oceanic woodlands, found on acid bark, especially on old Birch trees. The podetia are coarsely sorediate and without cups, like a poorly developed Cladonia polydactyla, but with highly dissected basal squamules and negative spot test and weak UV+ fluorescence. The basal squamules are similar to those of Cladonia squamosa, but this has different spot tests (K+ yellow or bright white UV+). The most distinctive feature, however, is red staining in the medulla, where the squamules have been damaged. This has been described as due to mite infection, but field observations suggests it is a response by the medulla of C. norvegica to any sort of damage.
Like a small cupless Cladonia polydactyla, but thalli with finely divided basal squamules, often with a reddish medulla and blemished with minute (×20 lens), scattered, superficial red spots, K+ purple, resulting from damage to the medulla. Apothecia absent and pycnidia rare in British populations; known to be ochraceous or pinkish in material from other localities. Thallus C–, K–, KC–, Pd–, UV+ bluish (weak) (barbatic acid).
It is suggested that the red spotting, a characteristic of this species in our region, is a reaction of this lichen to infestation by mites (probably Carabodes marginatus). This characteristic red-spotting is absent in many areas abroad, and certainly appears to be absent from some thalli in British populations. Molecular data are not available.
On mossy rocks and trunks of old trees, especially Betula, in old oceanic woodland; rare or overlooked.
Somerset (Exmoor), Wales (Cardigan, Snowdonia), Scotland (Kintyre to W. Ross).
Britain: Notable
Mainly recorded from quality humid oceanic woods
Pino-Bodas, R., Sanderson, N., Cannon, P., Aptroot, A., Coppins, B., Orange, A. & Simkin, J. (2021). Lecanorales, Cladoniaceae: including the genera Cladonia, Pilophorus and Pycnothelia. Revisions of British and Irish Lichens 19: 1-45. Link
Text by N A Sanderson, based Pino-Bodas et al (2021)