DNA barcoding uncovers two putative new species in Trachelyopterus (Siluriformes: Auchenipteridae).

Trachelyopterus is a cryptic genus within the Neotropical catfish family Auchenipteridae with a complex history of taxonomic revisions. Despite the notable morphological and genetic similarities among its species, some studies suggest that the genus harbours greater diversity than is currently recognized, including additional species yet to be formally described. One of the most widely used and effective approaches for investigating species delimitation and assessing biodiversity is DNA barcoding. The application of DNA barcoding has expanded considerably over the past decade, contributing significantly to the understanding of diversity across numerous groups of Neotropical fishes. Thus, in this study, we employed the DNA barcoding approach in both phenetic and phylogenetic contexts to investigate species diversity within the genus Trachelyopterus. Our sampling included four valid species previously identified based on morphology, collected from six hydrographic basins across the Neotropical region: Trachelyopterus galeatus, Trachelyopterus striatulus, Trachelyopterus porosus and Trachelyopterus coriaceus. Our results corroborate the validity of these four species and reveal two distinct lineages: one from the Araguaia River basin and another from the Pantanal in the Paraguay River basin, both of which may represent previously unrecognized species.