Genetic variability in four samples of Neoplecostomus yapo (Teleostei: Loricariidae) from the rio Paranapanema basin, Brazil

Four samples of Neoplecostomus yapo were analyzed through the allozyme electrophoresis technique in corn starch gel. The allozyme pattern was similar to those found in N. paranensis with 24 loci scored. Two samples (ribeirao Atlantico and ribeirao Ura) showed monomorphic bands for all 24 loci, whereas the other two (rio Verde and rio Fortaleza) showed 8.3% of polymorphic loci. The He genetic variability estimates for the rios Verde and Fortaleza populations were 0.0195 and 0.0179, respectively, too much inferior to the mean heterozygosity summed to species from the whole world (0.051). The Wright statistical values F-IS = 0.5181, F-IT = 0.5681 and F-ST = 0.1039 and the genetic distance of Nei values showed that the four samples are genetically very similar to each other and that there is homozygote excess in the polymorphic loci.