Allozyme variation in European silurid catfishes, Silurus glanis and Silurus aristotelis

The genetic structure and relationships of the two European catfish species, Silurus glanis (widely distributed in Europe) and Silurus aristotelis (endemic to Greece) were examined using 17 allozyme systems corresponding to 28 putative loci. The two species are well differentiated with fixed differences at five loci. Genetic distance values support inclusion of both species in the same genus. Average heterozygosities of 0.039 and 0.037 for native populations of the two species are slightly lower than previous average estimates for freshwater fishes. Greek S. glanis populations showed lower values of heterozygosity than the other European populations. A hypothesis for the evolution and dispersal of the two species is proposed, based on the estimated time of divergence and on the present distribution of these species.