Revisão taxonômica de Pinirampus Bleeker, 1858 (Siluriformes: Pimelodidae) em bacias neotropicais com uso de taxonomia integrativa

Abstract

Catfish of the genus Pinirampus have a wide distribution in the Neotropical region, occurring in the Amazon, Tocantins/Araguaia, Paraná, and Orinoco river basins. This study aimed to delimit and characterize possible populations of Pinirampus pirinampu through morphological and molecular (DNA barcoding) analyses. Specimens from various river basins, deposited in scientific collections, were used for the analyses. The mitochondrial gene Cytochrome Oxidase subunit I (COI) was used for molecular analysis, assessing nucleotide and haplotype diversity, genetic distance, molecular variance (AMOVA), and species delimitation using the methods: Assemble Species by Automatic Partitioning (ASAP), locMin, Bayesian Poisson Tree Process (bPTP), Generalized Mixed Yule Coalescent (GMYC), and phylogenetic relationships through Bayesian inference. Morphological data were obtained through morphometric measurements and vertebrae counts, using diaphanized specimens, dry skeletons, and X-ray imaging, followed by a linear discriminant analysis (LDA). A total of 130 nucleotide sequences of 536 bp were obtained, with no stop codons or insertion/deletion events (InDels). Fifteen haplotypes with geographic divergences were identified, particularly among the Amazon, Orinoco, Paraná, and Tocantins/Araguaia basins, with the presence of exclusive haplotypes. Genetic distance and molecular variance (AMOVA) analyses showed significant differentiation between populations (difference between groups = 98.31%; FST=0.98), suggesting strong genetic structuring, further supported by pairwise FST values. The Bayesian inference tree and dating analysis suggest that the Pinirampus araguayensis lineage diverged approximately 4.96 million years ago, while the Orinoco lineage separated around 3.08 million years ago, indicating diversification influenced by geological and ecological events. LDA and linear regression analyses suggested morphological variations, highlighting allometries in specific regions, complementing the molecular observations. Species delimitation analyses based on DNA barcoding and morphological approaches resulted in the proposal to revalidate synonymized species, such as Pinirampus araguayensis, P. barbancho, P. argentina, and the identification of a candidate species, Pinirampus sp1., from blackwater rivers draining the Guiana Shield. These findings emphasize the importance of integrated methodologies for a more accurate understanding of biodiversity, as well as for the conservation and sustainable management of genetically diverse species in Neotropical environments.