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.