Range-Wide Population Genetics and Hybridization in Pallid and Shovelnose Sturgeon

Threats to Pallid Sturgeon (PS) recovery vary range-wide, with a no recruitment in the northern part of the range and hybridization in the southern part.  The range of PS comprises four managements units (MU’S): Great Plains (GPMU), Central Lowlands (CLMU), Interior Highlands (IHMU) and Coastal Plains (CPMU).  More than 1000 field identified PS and 600 field-identified Shovelnose Sturgeon (SS) collected among all four MU’s were genotyped at 19 microsatellite loci.  PS and SS are genetically distinct in the GPMU, mostly distinct in the CPMU, and considerable introgressed elsewhere.  Nearly all field-identified PS in the CPMU are hybrids and backcrosses.  Analyses of allele frequencies among MU’s indicate no significant heterogeneity between the CLMU and IHMU but significant heterogeneity between the GPMU and CLMU/IHMU.  Since PS analyzed from the GPMU are likely as old as the dams that currently isolate them from the CPMU, this pattern is historical.  There were too few pure PS from the CPMU to test for heterogeneity among MU’s.  Based on these results, stocking of fish between the GPMU and CLMU/IHMU should be avoided and the threat of hybridization to recovery of Pallid Sturgeon should be investigated more thoroughly.