Genetic studies: Across North America - Across the Great Lakes
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Lake Erie sampling locations and primary genetic barriers for Walleye based on 10 microsatellite loci for 787 individuals. This map is interactive - selecting a point will show the genetic information for those samples.
Rex Meade Strange and Carol A. Stepien
Abstract: Discerning population genetic structure is challenging for highly vagile open water animals, as contemporary gene flow may obscure historic phylogeographic patterns. We examined genetic variation among all 10 major river and reef spawning groups of walleye (Sander vitreus vitreus) in Lake Erie for evidence of isolation by distance, segregation by physiographic partitions, and natal site fidelity using 10 nuclear DNA microsatellite loci. Results revealed that although most spawning groups were distinguishable, relationships did not correspond with physiographic basins or distances among localities. Bayesian analyses showed connectivity among some southern shore spawning groups, which included the largest-sized groups. Significant genetic divergence was discerned among walleye spawning in the river systems of eastern Lake Erie, as well as in two sites in western Lake Erie, along with marked isolation from Lake St. Clair. Population structure of Lake Erie walleye thus appears to reflect the interaction of two different intrinsic factors: isolation due to natal site fidelity that maintains patterns of divergence, and connectivity due to individuals that stray from their natal sites to spawn.
Fig. 1. Locations of the 11 primary walleye spawning sites in Lakes Erie and St. Clair and depiction of their genetic relationships.Solid circles denote sites with interconnectivity (i.e., the track), and open circles designate sites that significantly differ from all other groups. Heavy straight lines denote primary discontinuities in gene flow determined using BARRIER (Manni et al. 2004) and are sequentially numbered (I–III) in order of decreasing relative support. Grey regions (basins) and lines (rivers) inside modern-day Lake Erie depict its early development about 10 000 years before present (after Bolsenga and Herdendorf 1993).
Fig. 2. Pairwise relationship between genetic divergence and geographic distance expressed as FST(1 – FST)–1 versus the natural logarithm of kilometres. Linear regression and correlation coefficients are b = –0.003 and r = –0.12, respectively (Mantel P = 0.827).
Fig. 3. Estimated population composition from Bayesian STRUCTURE analysis for K = 3 groups (posterior probability = 0.998). Each individual is represented by a thin vertical line, which is partitioned into three colored segments that represent the individual's estimated group membership fractions. Black lines separate individuals from different spawning sites. Ten STRUCTURE runs at each K produced nearly identical individual membership coefficients. Moreover, K = 3 was verified by calculation of the rate of change of the likelihood distribution and graphing ∆K vs. K, following Evanno et al. (2005).
Genetic studies: Across North America - Across the Great Lakes
