Phylogeny and taxonomy of an enigmatic sterile lichen

Crustose, asexually reproducing taxa represent a large component of lichen biodiversity that is often overlooked and underestimated; as a result, remarkable potential remains for discovery of new species in this neglected, polyphyletic group. For this study, ITS and mtSSU rDNA sequences were analyzed in conjunction with chemical and anatomical data to understand the systematic placement of an enigmatic, sterile lichen. This species, despite references in the literature, and being known for over half a decade, has remained undescribed due to our inability to integrate it into a higher-level taxonomic framework using morphology alone. Here we demonstrate the utility of a systematic methodology that combines molecular and non-molecular characters to place and circumscribe species of asexually reproducing lichens that are typically sterile. Based on our analyses, the new species, Caloplaca reptans, shows phylogenetic and morphological affinities to a broad group of Caloplaca species with gray thalli, including the type species of the genus, C. cerina. This study highlights that the family Teloschistaceae is morphologically more diverse than previously understood, and contains elements that cannot easily be placed in known 'species groups.'