Genetic variability and evidence of founder effect in Hemiodus orthonops (Characiformes: Hemiodontidae) from the upper Paraná River basin, Brazil

Hemiodus orthonops is a small fish of the Hemiodontidae family, order Characiformes, with a maximum of 25 cm standard length. Until recently, H . orthonops was an endemic species from the Parana-Paraguay basin and it was absent from the upper Parana River basin. Since 2008, it has started to be collected in the upper Parana River, representing up to 10% of catches. Two population samples of H. orthonops from two localities of the upper Parana River basin (Porto Camargo and Porto Figueira) were analyzed using the allozymes electrophoresis technique. Twenty-one enzymatic loci were detected. The population sample from Porto Camargo displayed a genetic variability (He = 0.1061) higher than that from Porto Figueira (He = 0.0580) and homozygote excess in both of them. The F ST value (0.2081) indicated genetic structure. The excess of homozygotes in both samples was probably due to founder effect in the population.