Kanz, B., Brackel, W. v., Cezanne, R., Eichler, M., Hohmann, M.-L., Teuber , D. & Printzen, C. 2015. DNA barcodes for the distinction of reindeer lichens: a case study using Cladonia rangiferina and C. stygia. — Herzogia 28: 445–464.
Many groups of lichens are difficult to identify due to their phenotypical plasticity. Molecular methods are therefore increasingly used not only to elucidate phylogenetic relationships among taxa, but also to assign individuals to species. Most members of the genus Cladonia are conspicuous and frequently collected, but notoriously variable. At the same time the genus comprises species that have to be regularly monitored under EU legislation. A „DNA barcoding“ approach could thus be very helpful to correctly identify taxa. The internal transcribed spacer region of the ribosomal RNA repeat has been proposed as a universal barcoding marker for fungi. However, it has also been shown that data from this locus alone might be insufficient to reliably distinguish members of Cladonia. Taking the two similar species C. rangiferina and C. stygia as an example, we tested the suitability of ITS and five additional gene loci to distinguish species of Cladonia subgenus Cladina. Infraspecific variability was high in most of the investigated loci. Bayesian species delimitation using a multispecies coalescent approach based on multilocus DNA sequence data allowed us to separate the two species with high statistical support. The clustering of samples was also supported by phenotypic differences between the groups and a phylogenetic analysis. This allowed us to test the usefulness of single gene loci as barcoding markers on an objective basis. The only locus, for which minimum interspecific divergence exceeded maximum infraspecific variability in both species, was the small subunit of the mitochondrial ribosomal RNA repeat. Whether this locus should be suggested as an alternative or additional barcoding marker for the separation of Cladonia species needs to be tested with a broader taxonomic sample.