Arthonia lecanoricola
Anamorph: not known.
Teleomorph: ascomata visible as a dull black discoloration of the host apothecia, to 800 µm diam., irregularly rounded, matt, level with the hymenium of the host. Interascal tissue of paraphyses 2 µm diam., the end cell inflated to 2.5-3.5 µm diam., brown. Asci broadly clavate to saccate, staining wine-red in Lugol's iodine and after application of K, 8-spored. Ascospores 11–13 × 4–4.5(–5) µm (6-6.5 µm wide in the type material), broadly clavate, (1–) 2 (–3)-septate, the lower cell(s) distinctly narrower and more cylindrical.
Not formally assessed. In GB&I, known from four recent Scottish collections and could well be overlooked. Its host lichen has a relatively restricted distribution.
Parasitic in ascomata of Lecanora populicola and L. ? poliophaea. Both belong to the generic segregate Myriolecis/Polyozosia.
To date, found only in VC96 E Inverness on bark of Populus, and on maritime schists in VC52 Anglesey..