A preliminary study on phylogenetic relationship between five sturgeon species in the Iranian Coastline of the Caspian Sea

The phylogenetic relationship of five sturgeon species in the South Caspian Sea was investigated using mtDNA molecule. Sequence analysis of mtDNA D-loop region of five sturgeon species [Great sturgeon (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), Persian sturgeon (Acipenser persicus), Ship sturgeon (Acipenser nudiventris), Stellate sturgeon (Acipenser stellatus)] and DNA sequencing of two Escherichia coli cloned DNA fragments sized 758 bp and 922 bp was carried out. Sequence comparison of the mtDNA D-loop region between the five sturgeon species showed 100 % sequence identity. However comparison between a short (758 bp) and long (922bp) mtDNA D-loop region within Russian sturgeon showed a 5 bp differences. On the contrary a partial sequence of the mtDNA ND5 gene region showed high sequence and organic base variability in the five species. These results indicate that direct sequencing of ND5 gene provide more information for phylogenetic or population level studies in sturgeon species. The present study revealed a distinct classification among the five sturgeon species. On the basis of the phylogeny tree it is clear that a close evolutionary relationship exists between the great sturgeon and ship sturgeon that was verified in five phylogenetic trees. On the other hand a close resemblance was also seen between Persian and Russian sturgeon indicates that these two species have a closer evolutionary relationship. This study also showed a 2.2 % sequence divergence in sequence data for ND5 gene between Persian sturgeon and Russian sturgeon which indicated that these two species diverged from each other approximately one million years ago. However the verification of this calls for DNA sequencing of different genes.