Jupiaba acanthogaster (Eigenmann 1911)

is widespread in clear, running-water streams in the upper rios Paraguay, Tapajós and Araguaia-Tocantins drainages (Lima & Ribeiro, 2011). Jupiaba is a well corroborated monophyletic taxa (Zanata, 1997) and the remaining species of the group occurs in the upland amazonian tributaries from central Brazil. Similar distribution is reported for Knodus chapadae, from the upper portion of the upper rio Paraguay and from Tocantins basin (Ferreira, 2007). Our phylogeographyc analysis cared out in J. acanthogaster from 15 localities (Figs. 2-3) corroborate the hypothesis that tectonic origin of the upper rio Paraguay basin correspond to the most recent vicariant event in the evolutionary history of the area since samples from the rio Xingu basin are sister-group of a more inclusive clade encompassing the upper rio Tapajós and upper rio Paraguay. Thus, vicariance between the upper rio Paraguay and upper rio Tapajós is the least event in the biogeographic history of the group (Fig. 3).

The mean nucleotide diversity (ð) was 0.001152 and the mean haplotype diversity (h) was 0.512167; values for each locality are shown in Table 2. The obtained sequences corresponded to 28 haplotypes and any common haplotype was observed in all localities. The haplotype 15 was shared among three localities [rio Angelim, rio Paraguai (Corumbá) e rio Paraguai (Serra das Araras)], being the most frequent. The haplotypes 4-5, 6-7-8, 9-10-11-12-13-25, 16-27 and 19-20-21 were exclusive from a single locality: rio Salobro, ribeirão dos Veados, rio Culuene, rio Angelim, and rio Aricá-mirim, respectively.

Analysis of Molecular Variance (AMOVA) considering the three main groups identified (upper rio Xingu, upper rio Paraguay and upper rio Tapajós) showed that the variation are greater among the groups than within each group (Table 3). The values of pair-to-pair analysis of the FST shown the occurrence of a strong and significant division among localities (p<0.05), with valuesrangingfrom-0,03659 a 1,000 (datanotshown).Thevalues of pair-to-pair analysis of the FST considering the three groups (upper rio Xingu, upper rio Paraguay and upper rio Tapajós) also shown the occurrence of a strong and significant difference (p<0.05), ranging from 0.73615 to 0.97518 (Table 4).

The haplotype network (Fig. 4) confirmed the presence of three groups (upper rio Xingu, upper rio Paraguay and upper rio Tapajós), which are separated by 26 (rio Xingu x rio Paraguay), 38 (rio Xingu x rio Tapajós) and 13 (rio Paraguay x rio Tapajós) mutational steps. Localities within each group have related haplotypes, some even shared, corroborating the degree of relationship among them.