Contrasting morphological and DNA barcode-suggested species boundaries among shallow-water amphipod fauna from the southern European Atlantic coast

In this study we compared DNA barcode-suggested species boundaries with morphology-based species identifications in the amphipod fauna of the southern European Atlantic coast. DNA sequences of the cytochrome c oxidase subunit I barcode region (COI-5P) were generated for 43 morphospecies (178 specimens) collected along the Portuguese coast which, together with publicly available COI-5P sequences, produced a final dataset comprising 68 morphospecies and 295 sequences. Seventy-five BINs (Barcode Index Numbers) were assigned to these morphospecies, of which 48 were concordant (i.e., 1 BIN = 1 species), 8 were taxonomically discordant, and 19 were singletons. Twelve species had matching sequences (<2% distance) with conspecifics from distant locations (e.g., North Sea). Seven morphospecies were assigned to multiple, and highly divergent, BINs, including specimens of Corophium multisetosum (18% divergence) and Dexamine spiniventris (16% divergence), which originated from sampling locations on the west coast of Portugal (only about 36 and 250 km apart, respectively). We also found deep divergence (4%-22%) among specimens of seven species from Portugal compared to those from the North Sea and Italy. The detection of evolutionarily meaningful divergence among populations of several amphipod species from southern Europe reinforces the need for a comprehensive re-assessment of the diversity of this faunal group.Dans ce travail, les auteurs ont comparé la définition des espèces basée sur les codes a` barres de l’ADN avec celle issue de l’examen morphologique chez les amphipodes de la côte atlantique en Europe méridionale. Les séquences d’ADN de la région-code au sein de la sous-unité I de la cytochrome c oxydase (COI-5P) ont été obtenues pour 43 morpho-espèces (178 spécimens) recueillis le long de la côte du Portugal qui, combinées avec des séquences COI-5P déja` disponibles, ont produit des données représentant 68 morpho-espèces et 295 séquences. Soixante-quinze BIN (« Barcode Index Numbers ») ont été assignés a` ces morpho-espèces, dont 48 étaient concordants (i.e. 1 BIN = 1 espèce), 8 étaient discordants et 19 étaient uniques. Douze espèces avaient des séquences très semblables (distance