A DNA barcode reference library for endemic Ponto-Caspian amphipods.

Area of Science:

• Marine Biology
• Genetics
• Ecology

Background:

• The Ponto-Caspian region is a biodiversity hotspot for diverse crustacean radiations, particularly amphipods.
• Ponto-Caspian amphipods face threats in their native habitats and are invasive in European waters, necessitating accurate taxonomic knowledge for conservation and monitoring.

Purpose of the Study:

• To establish a DNA barcode reference library for Ponto-Caspian amphipods, covering nearly 60% of known species.
• To assess the congruence between molecular operational taxonomic units (MOTUs) and traditional morphological taxonomy.
• To identify taxonomic uncertainties and provide a foundation for improved monitoring and conservation efforts.

Main Methods:

• DNA barcoding using mitochondrial markers (COI and 16S).
• Definition of MOTUs using various methods, including distance-based approaches.
• Comparison of MOTU boundaries with species-level morphological taxonomy.

Main Results:

• A DNA barcode reference library was created for approximately 60% of Ponto-Caspian amphipod species.
• Morpho-molecular congruence varied by method, with 54-69% of species showing agreement.
• Incongruences included lumping distinct morphospecies into single MOTUs (7-27%) and splitting morphospecies into multiple MOTUs (4-28%).
• Distance-based MOTU definition without a priori thresholds yielded the highest congruence with morphology.

Conclusions:

• DNA barcoding is a valuable tool for resolving diversity and taxonomic uncertainties in Ponto-Caspian amphipods.
• Significant taxonomic work remains to be done to fully understand this fauna.
• The developed reference library enhances the study of European aquatic biota, supporting conservation and monitoring initiatives.