Parmelia discordans Nyl.

A species forming rosette-like thalli that later often develop an imbricate arrangement of brown, sometimes pruinose lobes 1–3 mm wide. It is morphologically very similar to P. omphalodes, and the variation of the two taxa overlaps considerably. The main diagnostic character is the presence of protocetraric acid in the medulla, which reacts Pd+ orange-red and K− or brownish. Lobaric acid is also consistently present.

Parmelia discordans grows on horizontal to vertical surfaces of siliceous stones and rocks. Most Czech records are from screes at elevations of approximately 550–800 m. The centre of its distribution is in the Brdy Highlands, where it may be relatively frequent at suitable sites. Outside the Brdy region, only two historical specimens were found during the herbarium revision: one from the ruins of Oheb Castle in the Železné hory Mts and the other from the vicinity of Chomutov. It is therefore a rare and local species in the Czech Republic. Parmelia discordans is known only from Europe, particularly from the northern and western parts of the continent.

Its taxonomic status in relation to P. omphalodes remains unresolved, and the two taxa could theoretically represent chemotypes of a single species.

Literature: Malíček J. & Ludvíková J. (2026): Does Parmelia omphalodes s. str. occur in the Czech Republic? – Bryonora 77: 1–13.

Ascomycota → Lecanoromycetes → Lecanorales → Parmeliaceae → Parmelia