Hidden diversity revealed by DNA barcoding of paralichthyidae fish along the caribbean and brazilian coast.

DNA barcoding based on COI sequences has been highly informative for the taxonomic assessment of many fish species due to its high rate of species identification. Accordingly, numerous studies have employed this method to encompass species checklists of different areas, assessment of cryptic diversity, biodiversity monitoring, and other applications. Furthermore, most of the success of COI DNA barcoding relies on a comprehensive database (BOLD Systems) that holds sequences and detailed records of millions of species and applies a system (BIN) that clusters short DNA barcodes to generate OTUs. Besides COI, the 16S rDNA has proven to be suitable for the molecular identification of several taxa, and the combination of both markers could be advantageous in investigating species composition in the Neotropics. The family Paralichthyidae comprises over 60 flatfish species. Most of them inhabit tropical areas and remain understudied. Here, we evaluated the diversity of Paralichthyidae species along the Brazilian coast through COI and 16S DNA barcodes. Combining our dataset with BOLD (COI) and GenBank (16S) public records, we conducted tree-based and genetic distance analyses along with BIN-based and species delimitation methods. Our results were consistent for both markers, and we identified eight species of paralichthyids among our samples with high confidence. Interestingly, our analyses indicate several cases where public records assigned to the same species might be sequences from multiple species. Therefore, we provide new records and occurrences and explore important issues regarding misidentification and putative cryptic diversity for several species.