Population Structure in the Ancient Octoploid White Sturgeon within and Among Drainages Revealed with Polysomic Microsatellite Markers

Historically, the examination of white sturgeon population structure has been limited by the highly duplicated nature of the species’ genome.  We report results from an examination of white sturgeon population structure within and among drainages using 13 polysomic microsatellite loci.  Low genetic diversity levels were observed in the endangered Kootenai River DPS and the high genetic diversity levels detected in regions with access to estuarine and marine habitat (Sacramento-San Joaquin, Lower Columbia, Lower Fraser rivers).  The greatest genetic divergence existed between the Kootenai River and all other regions.  Low levels of divergence were revealed among regions within the Columbia River and between regions with ocean access.  Patterns of population structure varied among drainages, with no population structure detected in the Sacramento-San Joaquin, hierarchical genetic structure detected in the Fraser, and a complex pattern of isolation by distance revealed in the Columbia/Snake.   Our results provided little support for the management of each impounded reach of the Columbia and Snake rivers as a distinct population.  The lack of population structure in the Sacramento-San Joaquin and the complex pattern of population structure observed in the Columbia suggested that the scale of spawning site fidelity in white sturgeon be reconsidered.