An integrated approach clarifies the cryptic diversity in Hypostomus Lacépède 1803 from the Lower La Plata Basin.

Hypostomus commersoni Valenciennes 1836, Hypostomus cordovae (Günther 1880) and Hypostomus laplatae (Eigenmann 1907) have been little studied since their original descriptions. This study shows a comprehensive review of these species from the Lower La Plata Basin, including their taxonomic history, distribution, color patterns, morphology, and ecological and molecular phylogenetic data. Morphological and phylogenetic analyses based on D-loop sequences suggested that H. commersoni can be separated into two subclades, or subgroups. Based on these results and on the non-overlapping distribution range of the two subclades, we conclude that they represent two distinct species, thereby revalidating H. spiniger. The results also suggest that H. paranensis should be considered as species inquirenda and H. cordovae as valid species. This integrated approach provides key information for assessing the conservation status and biogeographic aspects of the genus Hypostomus in the Lower La Plata Basin.

First DNA Barcode Reference Library for the Identification of South American Freshwater Fish from the Lower Paraná River.

Valid fish species identification is essential for biodiversity conservation and fisheries management. Here, we provide a sequence reference library based on mitochondrial cytochrome c oxidase subunit I for a valid identification of 79 freshwater fish species from the Lower Paraná River. Neighbour-joining analysis based on K2P genetic distances formed non-overlapping clusters for almost all species with a ≥99% bootstrap support each. Identification was successful for 97.8% of species as the minimum genetic distance to the nearest neighbour exceeded the maximum intraspecific distance in all these cases. A barcoding gap of 2.5% was apparent for the whole data set with the exception of four cases. Within-species distances ranged from 0.00% to 7.59%, while interspecific distances varied between 4.06% and 19.98%, without considering Odontesthes species with a minimum genetic distance of 0%. Sequence library validation was performed by applying BOLDs BIN analysis tool, Poisson Tree Processes model and Automatic Barcode Gap Discovery, along with a reliable taxonomic assignment by experts. Exhaustive revision of vouchers was performed when a conflicting assignment was detected after sequence analysis and BIN discordance evaluation. Thus, the sequence library presented here can be confidently used as a benchmark for identification of half of the fish species recorded for the Lower Paraná River.