The “Crustacean seas” in the light of DNA barcoding: a reference library for endemic Ponto-Caspian amphipods

Abstract

The Ponto-Caspian region is an endemicity hotspot that harbors several crustacean radiations, among which amphipods are the most diverse. These poorly known species are severely threatened in their native range, while at the same time they are invading European inland waters with significant ecological consequences. A proper taxonomic knowledge of this fauna is paramount for its conservation within and monitoring outside the native region. Here, we assemble a DNA barcode reference library for nearly 60% of all known Ponto-Caspian amphipod species. We use several methods to define molecular operational taxonomic units (MOTUs) based on two mitochondrial markers (COI and 16S) and assess their congruence with current species-level taxonomy based on morphology. Depending on the method, we find that 54–69% of species had congruent morpho-molecular boundaries. The cases of incongruence resulted from lumping distinct morphospecies into a single MOTU (7–27%), splitting a morphospecies into several MOTUs (4–28%), or both (4–11%). MOTUs defined by distance-based methods without a priori divergence thresholds showed the highest congruence with morphological taxonomy. These results indicate that DNA barcoding is valuable for clarifying the diversity of Ponto-Caspian amphipods, but reveals that extensive work is needed to resolve taxonomic uncertainties. Our study advances the DNA barcode reference library for the European aquatic biota, paving the way towards improved taxonomic knowledge needed to enhance monitoring and conservation efforts.

Cenozoic origins of the genus Calliarcys (Insecta, Ephemeroptera) revealed by Micro-CT, with DNA barcode gap analysis of Leptophlebiinae and Habrophlebiinae

“…just a morph or a hybrid. It is worth to stress that such misidentifications in open databases like GenBank and BOLD still persist, even if there are attempts for better data curation, and for removing obvious mistakes [32][33][34] . Given the number of EPT taxa and their importance for ecosystem health assessments, an inaccurate taxonomic assignment of DNA barcodes can seriously hamper the reliability of biomonitoring of water ecosystems based on molecular data.…”