Rhizocarpon reductum Th. Fr.

Rhizocarpon reductum is distinguished from other non-yellow species by the relatively small muriform spores and the common presence of stictic acid in the thallus. Following identification keys, specimens with well-developed spores may be misidentified as R. lavatum, which is macroscopically and ecologically different.

It is one of the most common brown Rhizocarpon species. It grows on acidic siliceous rocks and stones, often in humid microsites near the ground. It might also be found on anthropogenic substrates, such as walls, granite gravestones and rock monuments. In Europe, it is distributed at various elevations from the Mediterranean to Scandinavia. Likewise, it is abundant in the Czech Republic.

Ascomycota → Lecanoromycetes → Rhizocarpales → Rhizocarpaceae → Rhizocarpon