DNA barcoding confirms the occurrence of Rhamdia branneri and Rhamdia voulezi (Siluriformes: Heptapteridae) in the Igua?§u River Basin

摘要

DNA barcoding is a widely utilized molecular-based identification of species and taxonomic resolutions. Until recently, Rhamdia voulezi and Rhamdia branneri were considered species synonyms of Rhamdia quelen ; however, morphological and cytogenetic analyses have suggested the validity of distinct species. Due to the absence of molecular taxonomy of R. voulezi and R. branneri , the objective of this study was to test its validity through traditional DNA barcoding and the GMYC (General Mixed Yule Coalescent) COI-based analyses in 19 specimens from the Igua?§u River Basin. In both methodologies, three MOTUs (Molecular Operational Taxonomic Units) were identified based on the estimated optimum threshold (OT = 0.77). The average inter-MOTU distance (NJ, K2P) between R. branneri and R. voulezi was 1.4%, and 0% intra-MOTU distance in both species. The two species identified as R. branneri and R. voulezi showed correspondence with taxonomic and morphological identifications. With regard to R. quelen , the average intra-MOTU distance was greater than OT (2.7%), indicating that this species can be formed by different MOTUs. We suggest that molecular and taxonomic studies should be employed concurrently in R. quelen , to prevent contamination of wild species by hybridizations.