Phylogeographic analysis from freshwater fishes provide a natural link between both geological and biotic evolution of a region because fish dispersion depends on direct conexions among river basins, and the inter-conexion histories of river basins reflect the geological structure. Phylogeographic analysis of fish species widely distributed are very few studied. Fishes from Pseudoplatystoma genus, widely distributed through South América rivers, represent an important inland fisheries resource due to its big biomass and, besides they behave like predators in the ecosystems where they live. Thus, this project aims to characterize the population structure of species from Pseudoplatystoma genus, as well as examine the genealogical relationships and the geographic distribution of the haplotypes through its majority distribution in Brazilian territory, and interpret the observed patterns within the scope of phylogeography. DNA extractions will be performed from tissues (fins, preferentially) of individuals of the three species (P. corruscans, P. fasciatus and P. tigrinum) from five river basins: Amazonas, Itapecuru (Maranhão), Tocantins-Araguaia, São Francisco and Paraná-Paraguai. It will be amplified, by PCR, mitochondrial gene sequences (Cytochrome B and Cytochrome oxidase I), as well as part of D-loop sequence. In order to confirm the mtDNA estimated genealogies it will be used intron sequences from two nuclear genes (RAG1, Creatina Kinase). The fragments will be sequenced in both directions in an automated sequencer ABI 377 (Applied Biosystems Inc.). Statistical analysis will involve Maximum Parcimonia, Maximum Likelihood and Bayesian approach, using the Arlequim 2.0, PAUP 4.0b10 and MrBayes.
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