Microsatellite variation among River Sturgeons of the genus Scaphirhynchus (Actinopterygii: Acipenseridae): a preliminary assessment of hybridization

Abstract

Microsatellite variation from 13 disomic loci is reported for a total of 208 individuals of the genus Scaphirhynchus. This includes 105 individuals of the pallid sturgeon (Scaphirhynchus albus) from the lower Mississippi River, 11 pallid sturgeon from the Upper Mississippi and Missouri rivers, 65 shovelnose sturgeon (S. platorynchus) from the lower Mississippi River, six Alabama sturgeon (S. suttkusi), and 21 individuals of sturgeon identified as intermediate between S. albus and S. platorynchus. Results indicate that all five of the above population/species units are significantly differentiated from one another based on pairwise FST estimates. Locus Spl-7 was diagnostic for the Alabama sturgeon and serves to further differentiate this allopatric species from other Scaphirhynchus. Classification of genotypes with and without a priori designations failed to clearly delineate the species and intermediates in the latter case but was successful for the species but not in the intermediates in the former case. The presence of six unique alleles in five of the 21 morphologically ‘intermediate’ sturgeon examined requires additional evaluation but suggests that these individuals are possibly not the result of hybridization. We hope that raising these important issues will bring all stakeholders to the table to establish a concerted effort needed for both morphological and molecular analyses to adequately address the question of hybridization and the origin of the morphological variation in these fishes.