Molecular genetic analysis among subspecies of two Eurasian sturgeon species, Acipenser baerii and A-stellatus

Two species, the Siberian sturgeon, Acipenser baerii, and stellate sturgeon , A. stellatus, were studied using mitochondrial DNA (mtDNA) (D-loop, cytoc hrome b (cyt-b) and ND5/6 genes) sequencing to determine whether traditiona lly defined subspecies correspond to taxonomic entities and conservation ma nagement units. Initially several mtDNA regions for each taxon (A. baerii: 737 bp D-loop, 750 bp ND5, 200 bp ND6, and 790 bp cyt-b; A. stellatus: 737 bp D-loop and 600 bp ND5) were examined. The D-loop was the most variable r egion and was sequenced for 35 A. baerii and 82 A. stellatus individuals. N o fixed, diagnostic differences were found between any of the subspecies. G eographical structuring of haplotypes was observed within A. baerii, and ge ne flow estimates suggest isolation of the A. baerii baicalensis subspecies and the Yenisie and Lena River populations. No intraspecific subdivisionin g was found within the genetic data for A. stellatus. The use of the phylog enetic criterion (fixed diagnostic differences) for identifying conservatio n units is compared to the rationale and results of other methods. Overall, morphologically and geographically based subspecies designations within Ac ipenseridae may not directly correspond to the biological entities appropri ate for management and should not be used far conservation programmes witho ut genetic support.