Techniques in Lichenometry: Identifying the Yellow Rhizocarpons

Abstract

Species of Rhizocarpon subgenus Rhizocarpon are distinguished from each other based on differences in external thallus morphology, internal anatomy of fruiting bodies, and chemistry of intracellular and extracellular lichen substances. Differences in geographical distribution and ecology aid in identifying certain species. Using the procedures described in this paper, and keys such as that of J. Poelt (1988, this volume), it should be possible for a lichenometrist with no previous taxonomic experience to identify rhizocarpons to the section level with little difficulty, and to the species and subspecies levels under many circumstances. In regions where the subgenus has been inadequately studied (e.g., the Rocky Mountains of western North America), specimens having intermediate characteristics may prove difficult to identify using existing keys.