Genetic differentiation and phylogenetic relationships among Greek Silurus glanis and Silurus aristotelis (Pisces, Siluridae) populations, assessed by PCR-RFLP analysis of mitochondrial DNA segments

Mitochondrial DNA diversity of seven Silurus glanis populations (six from Greece and one from the Danube Delta) and three populations of the endemic Greek Silurus aristotelis was investigated. RFLP analysis of four regions of mitochondrial DNA (cytochrome b, D-loop, ND-5/6) amplified by PCR was used. Ten and nine haplotypes were found in S. glanis and S. aristotelis, respectively. No haplotype was shared between the two species. Significant geographical substructuring was observed in the distribution of haplotypes, with most populations possessing private haplotypes. These haplotypes can serve as genetic 'tags' and therefore warrant protection. Haplotype diversity was very low for all Greek S. glanis populations, possibly because the small size and large annual fluctuations of Greek inland waters do not support large fish populations. Nucleotide divergence was in the range of 0.00-0.52% among S. glanis populations, and 0.00-0.11% among S. aristotelis populations. Historical factors such as glaciations could account for these low values. The value of 6.75% sequence divergence of the two species refutes the classification of the two species in different genera, as proposed by some authors. This study constitutes the first attempt, based on mitochondrial molecular data, to address the complicated evolutionary history of the two species which belong to the widely distributed and economically important Siluridae family.