Cetrelia monachorum (Zahlbr.) W.L. Culb. & C.F. Culb.

(Figs 2; 5C; 9; 12)

It was not known before this revision as it was repeatedly misidentified before as either C. cetrarioides or C. olivetorum . It now turns out to be the most frequent Cetrelia species in Hungary (Fig. 9).

The presence of atranorin, imbricaric acid (major) ± perlatolic acid (minor), anziaic acid and 4-O-demethylimbricaric acid is characteristic. Cetrelia sayanensis Otnyukova, Stepanov & Elix (Otnyukova et al. 2009), a closely related species, has a slightly different chemical composition containing atranorin (minor), imbricaric acid (major), perlatolic acid (minor), divaricatic acid (minor)], anziaic acid (minor), 4-O-demethylimbricaric acid (minor), glomelliferic acid (trace) and loxodellic acid (trace). However, it has pustulate-capitate soralia with farinose soredia, while C. monachorum has only seldom laminal, capitate soralia and is further characterised by coarse soredia, 52.7± 5.6 µm in Hungarian samples [vs (35)40-55 µm diam. in Obermayer & Mayrhofer (2007)], small (50-150 µm), raised pseudocyphellae on upper cortex, but very rare or lacking on lower cortex.

Cetrelia monachorum is most frequently collected from rocks (70%), but also grows on Quercus (14%), Fagus (6%), Carpinus (2%), Acer pseudoplatanus L. (1%) and on unidentified bark (7%) between 100-1000 m a.s.l. reaching the highest possible elevation in Hungary (Mátra Mts). The species is proposed for the category near threatened (NT) in Hungary.