Comparação molecular de piranhas dos gêneros Serrasalmus e Pygocentrus (Characiformes, Serrasalmidae) das bacias do alto rio Paraná, alto rio Paraguai, rio Tocantins e rio São Francisco

• Autor(a) principal: Bignotto, Thaís Souto
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1338
• topic: Piranha (Serrasalmus e Pygocentrus) - Complexo de espécies - Alto rio Paraná - Alto rio Paraguai - Rio Tocantins e rio São Francisco; Diferenciação molecular; Marcadores mitocondriais - D-loop - Citocromo c oxidase I e citocromo b; Ciências Agrárias; Agronomia

Fish known as "piranhas" belong to the family Serrasalmidae, order Characiformes, and comprise four genus (Serrasalmus, Pygocentrus, Pristobrycon and Pygopristis). Several phylogenetic and systematic studies that include this group of fish have been developed, although much remains unclear. The monophyletic condition of Serrasalmus was not successfully accomplished and relationships among Serrasalmidae taxons were not yet established. Hence, this work aims to characterize different piranhas species (Serrasalmus maculatus, S. marginatus, S. eigenmanni, S. rhombeus, S. brandtii, Serrasalmus sp., Pygocentrus nattereri and P. piraya) from Upper Paraná River, Upper Paraguai River, Tocantins River and São Francisco River basins in an attempt to contribute with the comprehension of their genetic and phylogenetic relationships. DNA mitochondrial regions - control region (D-loop) and cytochrome b and cytochrome c oxidase I genes - were sequenced and analysed. Phylogenetic analysis of neighbor-joining, maximum-likelihood and Bayesian approach were performed. Piranhas species inhabiting more than one hydrographic basin are genetically differentiated according to their respective localities. Pygocentrus nattereri populations from Tocantins and upper Paraguai River basins are genetically different from each other. The same occurred to Serrasalmus maculatus populations from Tocantins and Paraná-Paraguai River basins. Pygocentrus nattereri population from Tocantins River differed from upper Paraguai River population by low values of genetic distance, which characterizes differences between populations of only one species that is broadly distributed. On the other hand, S. maculatus populations presented values of divergence usually found for different species. This can suggest that there is a S. maculatus complex of at least two species on the localities sampled. Shared mitochondrial haplotypes were identified between Serrasalmus sp. and S. maculatus both from Tocantins River basin, indicating that or these fish belong to one same species or hybridization processes occur frequently in this basin. Low values of genetic distances were identified between S. marginatus and S. rhombeus, indicating that these species are very close to each other. Moreover, S. rhombeus was split into two clades by values very similar to those found between S. rhombeus and S. marginatus. This also suggests the occurrence of a species complex. The biogeographic pattern found for the analyzed piranhas species seems to corroborate the geological and hydrological events previously documented in the literature. Basins separations and headwater capture events between different rivers systems that occurred in the past seem to have strongly influenced the distribution of piranha species.