DNA Barconding do gênero Schizodon (Characiformes, Anostomidae)

Abstract

Fish of the Schizodon genus have important representation in the largest South American basins. Historically they underwent through several taxonomic revisions, due to their high phenotypic plasticity and the ontogenetic characters found among the species of this group. The goal of this work was to evaluate the congruence between the molecular units (MOTUs) and the nominal species currently valid, using the DNA barcoding and coalescent methods. DNA extraction, amplification and analysis of the mitochondrial COI region from 68 samples were performed; additionally, 19 sequences available on the BOLD system were added to the analyses. The CodonCode Aligner program was used to edit the sequences and alignment. The genetic distances were calculated in the MEGA 7 software, using the K2P model (Kimura 2-Parameters). For the distance-based species delimitation, the DNA barcoding method was used with three different values of thresholds (2%, 1.4% and 1%). Although evidencing different numbers of MOTUs, the results were congruent in suggesting a possible synonymy of S. jacuiensis and S. platae. With the thresholds 1.4% and 1%, S. vittatus was subdivided into two MOTUs, evidencing the existence of a potential cryptic species. These results were corroborated in the GMYC (Generalized Mixed Yule-coalescent) species delimitation analysis. Thus, the findings of this work show that there are disagreements between the molecular units and the currently valid taxonomy for the genus. This indicates that an extensive taxonomic revision, using morphological and molecular tools, which include different genes, is still needed for a better decision on the taxonomic status within the Schizodon genus.