Rhizocarpon umbilicatum forms a continuous chalky white and pruinose thallus with inconspicuous prothallus. Apothecia are black and immersed, with a thick, grey-pruinose proper margin and are unevenly distributed. The similar R. petraeum is distinguished by larger and more-septate spores and apothecia arranged in circles. However, the circular arrangement was recorded in only 30% of revised specimens (Ihlen 2004). Underdeveloped R. petraeum with unevenly arranged apothecia and immature spores can be easily misidentified, as was the case of the finish herbarium material originally labelled R. umbilicatum (Ihlen 2004).
The species has a circumpolar distribution. It grows on natural calcareous rock substrates. It is scattered throughout Europe, including the British Isles. In central Europe, it is considered a montane, even arctic-alpine element only rarely found at lower elevations (e.g., Wirth et al. 2013, Nimis et al. 2018). Within central Europe, it is more abundant in the Alps and western Carpathians (e.g., Nimis et al. 2018, Lisická 2005). In the Czech Republic, R. umbilicatum is very rare and recent records require revision.
Literature: Nimis P. L., Hafellner J., Roux C., Clerc P., Mayrhofer H., Martellos S. & Bilovitz P. O. (2018): The lichens of the Alps – an annotated checklist. – Mycokeys 31: 1–634. Ihlen P.G. (2004): Taxonomy of the non-yellow species of Rhizocarpon (Rhizocarpaceae, lichenized Ascomycota) in the Nordic countries, with hyaline and muriform ascospores. – Mycological Research 108: 533–570. Lisická E. (2005): The lichens of the Tatry Mountains. – Veda, Bratislava.taxonomic classification:
All records: 11, confirmed 2. One click on a selected square displays particular record(s), including their source(s).