DNA barcoding of native Caucasus herbal plants: potentials and limitations in complex groups and implications for phylogeographic patterns

DNA barcoding rapidly became a useful complementary tool in floristic investigations particularly for identifying specimens that lack diagnostic characters. Here we assess the capability of three DNA barcode markers (chloroplast rpoB, accD and nuclear ITS) in correctly species assignment in a floristic survey on Caucasus. We focused on two herbal groups with potential for ornamental applications, namely orchids and asterids. On these two plant groups we tested whether our selection of barcode markers allows identification of the “barcoding gap” in sequence identity and to distinguish between monophyletic species when employing distance-based methods. All markers successfully amplified most specimens, but we found that rate of species-level resolution among selected markers largely varied in the two plant groups. Overall, for both lineages, plastid markers had a species-level assignment success rate lower that nuclear ITS marker. The latter confirmed in orchids both the existence of a ba...