Genetic structuring of Salminus hilarii Valenciennes, 1850 (Teleostei: Characiformes) in the rio Paraná basin as revealed by microsatellite and mitochondrial DNA markers

Genetic variation of Salminus hilarii was assessed by screening microsatellite loci and mitochondrial D-loop DNA across four sampling in the upper rio Paraná basin of Brazil. Genetic diversity - measured as mean expected heterozygosity (0.904) and mean number of alleles across populations (13.7) - was reasonably high. Differentiation of microsatellite allele frequencies among populations was shown to be low but significant by AMOVA Φ ST (0.0192), and high by D EST (0.185). D-loop variation was high, with haplotypic diversity of 0.950 and nucleotide diversity of 0.011. Mitochondrial DNA-based estimates for population differentiation were high, with an overall Φ ST of 0.173. The results of tests of nuclear and mitochondrial variation yielded no unequivocal inference of historical demographic bottleneck or expansion. Genetic differentiation observed among S. hilarii populations in the rio Grande may be caused by a combination of historical differentiation and recent gene-flow disruption caused by the dams followed by reproduction of isolated spawning assemblages in mid-sized tributaries of the respective reservoirs. We present spatially more intensive sampling of S. hilarii populations across the rio Paraná basin in order to more effectively distinguish between historical and contemporary differentiation.