Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

3.  GENETIC DISCRIMINATION OF PALLID (SCAPHIRHYNCHUS ALBUS) AND SHOVELNOSE STURGEONS (S. PLATORHYNCHUS) USING DNA MICROSATELLITE MARKERS

Aaron W. Schrey*, Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, Life Science II Room 173, 1125 Lincoln Drive, Carbondale IL 62901-6511; Phone 618-453-3815: FAX 618-536-7761; aschrey@siu.edu

Edward J. Heist, Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, Life Science II Room 173, 1125 Lincoln Drive, Carbondale IL 62901-6511; Phone 618-453-4131: FAX 618-536-7761; edheist@siu.edu

Discriminating pallid (Scaphirhynchus albus) and shovelnose sturgeons (S. platorhynchus) with morphological and molecular data has been problematic due to the presence of morphological intermediates, allometric growth, and the absence of fixed genetic differences in any of the molecular markers applied to date. We report on the use of assignment testing using DNA microsatellite genotypes to demonstrate that pallid and shovelnose sturgeon gene pools are distinct and that multilocus genotypes can be used to discriminate between the species. Genetic variation was screened at multiple microsatellite loci for putative pallid and shovelnose sturgeons. The markers used were highly variable (6 to 37 alleles, mean observed heterozygosity = 0.71). Initially, a model-based clustering of the genetic data alone (no a priori species identifications) demonstrated the presence of two genetic clusters largely concordant with morphological identifications of pallid and shovelnose sturgeons. Likelihood-based assignment testing utilizing allele frequencies derived from morphologically identified specimens also provided a high degree of success in assigning individuals to the correct species. These data suggest that assignment testing with multiple microsatellite loci could provide genetic-based discrimination of pallid and shovelnose sturgeons at all life-history stages. We expect this methodology to be useful for several aspects of pallid sturgeon recovery including the selection of pallid sturgeon broodstock and the identification of pallid sturgeon larvae in field samples.