Type studies in the<i>Rhizocarpon geographicum</i>group (<i>Rhizocarpaceae</i>, lichenized Ascomycota)

Abstract

Abstract As part of a comprehensive revision of the Rhizocarpon geographicum species group using molecular and morphological approaches, we examined the name-bearing types of 15 species. We report ambiguities and inconsistencies with the reported features of some type specimens, original descriptions, and circumscriptions employed in keys for the identification of taxa within the complex. The reporting of chemical reactions and some morphological characters was found to be inconsistent and likely to lead to errors of identification. This is unfortunate in view of the widespread use of the complex in glaciology for lichenometry. Issues surrounding the typification of the basionym Lichen geographicus are clarified, and the epitype is illustrated. The complex nomenclatural situation regarding the name Rhizocarpon lecanorinum and its typification is also made clear. The examination of the anatomical and morphological characters presented here needs to be considered together with molecular phylogenetic information to provide a more informed new taxonomy of the group.