Delimitação de espécies-linhagens do gênero Pseudoplatystoma (Siluriformes: Pimelodidae) e estimativa da variabilidade genética de P. punctifer

Abstract

The catfishes of the genus Pseudoplatystoma play an important role as top predators in freshwater ecosystems in the neotropical region. The species of this genus are important fishing resources and have a high commercial value in their area of distribution. For a long time, the richness of species of this genus was neglected, where only 3 species were recognized. However, after the morphological revision of the genus, the number of species increased to eight. In the first study of molecular systematics, the species richness was again neglected, as only four distinct species were recognized for the genus: Pseudoplatystoma magdaleniatum, Pseudoplatystoma corruscans, Pseudoplatystoma tigrimun (sensu lato) and Pseudoplatystoma fasciatum (sensu lato). Thus, the first chapter of this study aimed to: Test the mitochondrial markers cytochrome oxidase I (COI) and the control region (RC) as tools to assess species diversity for the genus Pseudoplatystoma based on the methods of delimiting specieslineages single locus. The COI was not efficient in delimiting the different morphospecies, where only five species-lineages were delimited. However, the RC based on the GMYC (Generalized Mixed Yule Coalescent) and bGMYC (Bayesian implementation of GMYC) methods, delimited 9 lineage species, of the 8 morpho-species described for the genus Pseudoplatystoma, thus recognizing the taxonomic diversity of the genus. Until integrative taxonomy studies are carried out to define the taxonomic status of the species of Pseudoplatystoma, we suggest that conservation measures (if necessary) be carried out independently for these nine lineage species identified in this study. For the second chapter: Using microsatellite and mitochondrial (COI) markers, to estimate diversity, genetic differentiation, and gene flow for Pseudoplatystoma punctifer, between sub-basins of the Madeira and Mamoré/Guaporé rivers. It was tested whether the rapids functioned as barriers that limit the gene flow for this species. Three population groups were identified, one representing individuals from the Mamoré/Guaporé sub-basin (upstream of the rapids) and the other two representing individuals from the lower Madeira sub-basin (downstream of the rapids). Some factors may be contributing to the genetic differentiation observed in the lower Madeira and Mamoré / Guaporé sub-basins. Among these factors, we highlight the isolation by distance (given that the species is partially migratory), the restricted gene flow, and the hydrochemical and ecological heterogeneity throughout the study area. Additional studies are needed to understand the pattern of genetic differentiation associated with different types of water for P. punctifer in the Amazon basin. Considering the economic and ecological importance of P. punctifer, we believe that the results of this study can become an important contribution to subsidize adequate conservation and management measures for these species in the sub-basins of Madeira and Mamoré/Guaporé.