Diversidade críptica em Hypostomus Lacépède, 1803 (Siluriformes : Loricariidae), de tributários das bacias do Alto Rio Paraguai, Guaporé, Juruena, Madeira e Araguaia

Abstract

Hypostomus (Loricariidae, Hypostominae) is a diverse group in number of species and, despite being considered monophyletic, the relationship between the individuals that compose it is complex. Many of its representatives present morphological similarities and a high genetic variability, suggesting the existence of species complexes within the genus. In addition, the occurrence of phenotypic plasticity has already been observed in some species, which makes it even more difficult to resolve taxonomic uncertainties within the group. In view of this, the present work aims to analyze, based on DNA barcoding, specimens of Hypostomus collected in some regions of the watersheds of the Upper Paraguay River, Guaporé, Juruena, Madeira and Araguaia, providing subsidies to understand what is the real diversity of representatives of this genus. The dataset analyzed is composed of 57 specimens, identified a priori in 15 species based on morphological characters. All samples were submitted to molecular techniques of DNA extraction, Polymerase Chain Reaction (PCR) and sequencing. Subsequently, genetic analysis methods were carried out to delimit the species by genetic distance (ASAP, OT) and by coalescence (PTP and GMYC). The final alignment of all sequences generated fragments of 614 base pairs. The results revealed that, of the 15 species classified a priori on a morphological basis, 13 to 16 MOTUs were identified, depending on the delimitation method used, with 13 MOTUs being evidenced by ASAP, 16 by Optimal Threshold, 14 MOTUs by PTP and 15 MOTUs by GMYC. After a consensus analysis, six MOTUs considered as probable new species were identified, which are: Hypostomus sp.1 and Hypostomus sp.2 from the Branco river affluent of the Guaporé, Hypostomus sp.3 from the Juruena river, and Hypostomus sp.4 from the Araguaia river, Hypostomus sp.5 from the Cabaçal river Paraguay basin and Hypostomus sp.6 from the Branco river in the Guaporé basin in Rondônia. The species H. latirostris (Cuiabá river) and H. cf latirostris (Coxipó river), presented incongruent results, since the ASAP and PTP analyzes grouped these species in a single MOTU; in the analysis with GMYC, which also presented an incongruous result, only two specimens of the 13 H. latirostris sequences clustered with H. cf latirostris. the analysis of the Great Threshold was the closest to the nominal designation, delimiting the species as being distinct species. The Optimal Threshold (OT) value was 1.53%; this value delimits the intra and interspecific genetic distances. The mean interspecific genetic distance ranged from 0.85% between H. latirostris from the Cuiabá river and H. cf latirostris from the Coxipó do Ouro river (both from the Paraguay river basin), to 9.15% between Hypostomus sp.2 from the Branco river and H. cf hemicochliodon from a tributary of the Madeira and Juruena rivers. The intraspecific variation ranged from 0% in H. cf latirostris from Coxipó do Ouro and five other species, to 0.41% in H. latirostris. The results presented show that, for the locations studied, the number of known species for the genus is underestimated, requiring further studies to know the real diversity of Hypostomus. In addition, the use of the DNA Barcode technique is efficient in the search for tools to better diagnose this complex group of Neotropical fish.