Cladonia strepsilis
A large Cladonia, of damp and wet heathland and moorland, mostly occurring as sterile mats of basal squamules, with a distinctive mottled green-bronze colour when dry, pale apple green when wet, rarely with podetia. With a characteristic C + green spot test.
Podetia to 1 cm tall, rare, irregular or turgid-branched, ± uniformly corticate, often squamulose and fissured, sometimes areolate, unbranched or branched near the tips, with perforate axils. Basal squamules dominant, to 4 mm long, rounded or ± elongate, indented, often contiguous, forming cushions; upper surface bronze-green, pale apple green when wet, white below. Rarely the squamules support delineated heaped solaria; a distinctive feature but not of any apparent taxonomic significance. Apothecia dark brown, rare. Pycnidia brown, frequent on basal squamules. Thallus C+ bright emerald green, K–, KC–, Pd+ yellow, UV+ whitish (baeomycesic and squamatic acids, strepsilin).
Forming a monophyletic grouping within clade Perviae (Stenroos et al. 2019). Readily distinguished by the unique C+ emerald green reaction (strepsilin), the combination of cushions of basal squamules of a beaten rusty bronze colour when dry, pale apple green when wet and tendency to grow in wetter habitats than most other species. Beware that applying C to brown Cladonia squamules results in a persistent dull green colour as the brown colour is removed; not to be confused with the fleeting bright emerald green reaction of Cladonia strepsilis. Sorediate specimens conspicuous yellow-green heaped up soralia are occasional in the New Forest (S. England, Hants) and probably elsewhere.
On damp to wet very acid humus in moorland and heathlands. Most typically on thin peat over rock or erroded blanket bog in the uplands and in open patches in low productivity wet and humid heath in the lowlands. Recently it was discovered in open patches in lichen rich montane Racomitrium lanuginosum – Carex bigelowii moss heath in the Lake District. Avoids permanently wet peat, but can survive some imersing in temporary flooded pans. Absent from dry sandy heaths. A light demanding species, often dependant on grazing, burning or occasional disturbance to prevent loss to over shading. A highly fire resistant species, which often survives cool fires as whitened squamules, which sprout new green squamules. Like Pycnothelia papillaria, it prefers humus rich soils, typically firm humus and it is absent from both bare mineral soil or loose fibrous humus, so does not benefit in the short term from soil disturbance in lowland heaths. Strong colonisation of features such as WWII gravel pit bases in the New Forest, however, suggests that colonisation will occur if the ground remains open for decades allowing humus development.
Cladonia strepsilis has a distinct British distribution, shared by other heathland species such as Pycnothelia papillaria and Cladonia zopfii. It is frequent in the Scottish Highlands and locally frequent in southern lowland heathland south of the River Thames but rare in the uplands between. Cladonia strepsilis, however, is more frequent in the Lake District and North Wales than these species but it is still very rare in other moorland areas. In these upland areas this is most likely due to the rarity of very low productivity habitats such as the heavily leached and pre glacial soils of the southern heathlands and shallow humus over rock habitats found in other upland areas. Recently a strong decline has been detected in lowland heaths outside of the New Forest, related to a reduction in grazing and a lack of controlled burning of heaths. It is still abundant in the New Forest, where a recent systematic survey recorded Cladonia strepsilis from 73 out of 100 1km grid squares sampled.
In Ireland it is widespread in moorland to the west but rare in the east.
This species is highly threatened across the European lowlands and is listed as Vulnerable in Netherlands and Denmark, and is also suffering a severe decline in lowland England, except in the New Forest. In the New Forest it is still widespread and locally abundant with traditional heathland management providing frequent well lit hard humus surfaces. The main positive factors are extensive but locally heavy range grazing, controlled burning and accidental and occasional soil disturbance. Air pollution is also implicated is some losses but it has been equally lost from clean air areas where traditional management or suitable periodic disturbance has stopped.
Not threatened in the northern uplands but could decline with abandonment of tradition moorland management.
Ahti, T. & Stenros (2013) Cladonia. In: Nordic Lichen Flora, Volume 5 Cladoniaceae (ed. T. Ahti, S. Stenros & R. Moberg) 8-86. Uppsala: University of Uppsala.
Aptroot, A., van Herk, K. & Sparrius, L. (2011) Korstmossen van Duin, Heide en Stuifzand. Bryologische en Lichenologische Werkgroep van de KNNV
James, P. W. (2009) Cladonia P. Browne (1756). In: The Lichens of Britain and Ireland (C. W. Smith, A. Aptroot, B. J. Coppins, A. Fletcher, O. L. Gilbert, P.W. James & P. A. Wolseley, eds): 309 – 338. London: British Lichen Society.
Pino-Bodas, R., Sanderson, N., Cannon, P., Aptroot, A., Coppins, B., Orange, A. & Simkin, J. (2021). Lecanorales: Cladoniaceae [revision 1], including the genera Cladonia, Pilophorus and Pycnothelia. Revisions of British and Irish Lichens 26: 1-45.
Sanderson, N. A. (2016) The New Forest Heathland Lichen Survey 2011 – 2015. A report by Botanical Survey & Assessment to Natural England, Forest Enterprise & The National Trust. Link.
Stenroos, S., Pino-Bodas, R., Hyvonen, J., Lumbsch, H.T. & Ahti, T. (2019). Phylogeny of the family Cladoniaceae (Lecanoromycetes, Ascomycota) based on sequences of multiple loci. Cladistics 35: 351–389 [publ. 2018].
Text by Neil A Sanderson, based on James (2009) & Pino-Bodas et al (2021)