Usnea dasopoga (Ach.) Nyl. and U. barbata (L.) F. H. Wigg. (Ascomycetes, Parmeliaceae) are two different species: a plea for reliable identifications in molecular studies

Using molecular data to delimit species or reconstruct their evolutionary history is now widely used across all organisms. However, such analyses can suffer from poor or false specimen identifications leading to incorrect conclusions. Here we show that the use of misidentified specimens in a phylogenetic framework resulted in questionable conclusions in a previously published study (Mark et al. 2016). Using morphological, chemical and statistical analyses on the specimens used in that study, we found support for Usnea barbata and U. dasopoga being morphologically and anatomically distinct species with separate clusters in the molecular phylogeny. Furthermore, our revision of specimen identifications refutes the synonymization of U. substerilis with U. lapponica. In conclusion, we discuss the issue of correct identification of voucher specimens in DNA databases and conclude with some general suggestions to avoid false specimen identifications in phylogenetic studies.