Population Genetic Structure of Smallmouth Bass Across North America: Patterns From Two Genomes

Analysis of population genetic relationships reveals the signatures of ongoing processes such as spawning behavior and migration, and historical events such as vicariance and climate change. This study provides a dual genome analysis of population genetic patterns of spawning smallmouth bass across 13 locations-including all Great Lakes and the Mississippi, Ohio, St. Lawrence, and Hudson rivers -using eight nuclear DNA microsatellite loci and mtDNA cytochrome b sequences. Null hypotheses are (1) genetic variation is not significantly partitioned among watersheds, lakes, rivers, and basins and (2) there is not a significant difference between mitochondrial and nuclear DNA patterns. Results discern genetic demarcations across the range, and pronounced differences even among closely spaced riverine sites. Sampling sites contain a substantial proportion of full-sibling adults, suggesting natal site fidelity and relatively low dispersal. Population genetic origins trace to recolonization patterns from glacial refugia, which have been maintained through present day. Relationships follow a broadscale genetic isolation by geographical distance pattern, but those within lakes and proximate river sites do not. The latter appear influenced by homing and site fidelity.