Draft
Thallus continuous, becoming areolate in the centre, forming clearly delimited patches, concentrically zoned, grey; prothallus fibrous, grey. Apothecia to 1.5 mm diam., aggregated in small groups, ± immersed in the thallus; thalline margin entire to irregularly contorted, persistent, often pruinose and including numerous crystals; disc pale brown to pale yellow-brown, flat, grey-white pruinose when young; epithecium colourless to brown, interspersed with numerous granules; hymenium 45–75 µm tall; hypothecium with small granules; paraphyses 1–2 µm diam., sparsely branched, apices not swollen. Ascospores 10–16 × 6–9 µm. Thallus C–, K–, KC–, Pd–, UV– (2,5-dichlorolichexanthone).
Listed as a member of the Lecanora dispersa group (i.e. Myriolecis) by Edwards et al. (2009), and sequences of material in RBG Edinburgh confirm that placement. The combination into Myriolecis was formally made in Cannon et al (2022). Possibly confused with Lecanora albella, Glaucomaria carpinea (in which the apothecia are either C+ yellow or Pd+ rust red) and pale-fruited forms of L. chlarotera s. lat..
It is sometimes host to Candelariella superdistans, and Arthonia lecanoricola often causes blackening of the disc.
On smooth bark, trunks and twigs of Aspen; rare but locally abundant.
East central & N.E. Scottish Highlands, apparently extinct in England (E. Norfolk, Coltishall)
Widespread on Aspen in the eastern Highlands, showing a marked sub-oceanic distribution. Long Regionally Extinct in eastern England but shoul be looked out for on aspen and other poplars in this area.
Britain: Notable
Scotland: Priority Taxon for Biodiversity in Scotland
Cannon, P., Malíček, J., Ivanovich, C., Printzen, C., Aptroot, A., Coppins, B., Sanderson, N., Simkin, J. & Yahr, R. (2022). Lecanorales: Lecanoraceae, including the genera Ameliella, Bryonora, Carbonea, Claurouxia, Clauzadeana, Glaucomaria, Japewia, Japewiella, Lecanora, Lecidella, Miriquidica, Myriolecis, Palicella, Protoparmeliopsis, Pyrrhospora and Traponora. Revisions of British and Irish Lichens 25: 1-83.
Edwards, B., Aptroot, A., Hawksworth, D.L. & James, P.W. (2009). Lecanora. In Lichens of Great Britain and Ireland (Smith, C.W., Aptroot, A., Coppins, B.J., Fletcher, A., Gilbert, O.L., James, P.W. & Wolseley, P.A. eds): 465–502. London: British Lichen Society.
Text by Neil A Sanderson based on Cannon et al (2022)