Abstract
Understanding the spatial context of genetic variation for species at risk is important for effective management and long-term survival of the species. We use multilocus microsatellite data to investigate the population genetic structure of the spotted gar (Lepisosteus oculatus) across its northern range edge in Canada. We then compare these northern individuals with samples taken from the southern core of the species range. For the northern samples, significant genetic differentiation among groups of individuals forming two major genetically distinct populations, and as many as 7–9 smaller subpopulations, was recovered using hierarchical Bayesian assignment methods and non-equilibrial discriminant function analyses. Spatial genetic variation is present, particularly at higher hierarchical groupings; however, some population admixture at sites is evident and is indicative of dispersal and gene flow among some locations or shared ancestry. Gene flow estimates among populations and subpopulations is very low, ranging from essentially complete isolation to as high as 5 %—suggesting that mechanisms in addition to geographic isolation are operating to create genetic structure. In Lake Erie, the physical isolation of Point Pelee appears to confer distinct genetic differentiation for those populations and provide a source of genetic variation for Lake Erie proper when breaches to the barrier beach occur. Results indicate that the northern edge populations are distinct from southern populations and should be conserved to maintain the overall genetic diversity of this species. Additionally, the asymmetrical genetic connectivity among the Point Pelee and Rondeau Bay sites highlights the sensitivity of Point Pelee to environmental perturbation and habitat degradation.
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Acknowledgments
We thank Hank Bart, David Rowe, and Mathew Spickard for providing us with tissue samples. We also thank Aaron Simpson, Ben Meunier, Krista Lajevardi, Solomon David, Tim Clay, Mark Suchy, Cynthia Fox, Allyse Ferrara, Bob Hrabik, and Jason Crites for assistance with field collections and Thom Heiman for assistance with aging of the specimens. Funding was provided by the Fisheries and Oceans Canada Species at Risk Program awarded to NEM and NSERC funding to DDH. The basemap used to create Fig. 1 was provided by freevectormaps.com. We thank our anonymous reviewers for their constructive comments that have helped to improve the manuscript.
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10592_2015_708_MOESM1_ESM.tif
Supplementary Fig. 1. Population genetic structure of spotted gar determined by Bayesian clustering assignment using STRUCTURE without location information, showing 10 resolved populations throughout North America. Southern group population substructure for K = 2 and K = 3, and northern group substructure for K = 2 and K = 3 are also shown along with Lake Erie (Point Pelee and Rondeau Bay) substructure. The coloured bubbles correspond to the respective recovered population, with effective number of breeding individuals (N b) in italics; arrows indicate direction of gene flow with accompanying migration estimates
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Glass, W.R., Walter, R.P., Heath, D.D. et al. Genetic structure and diversity of spotted gar (Lepisosteus oculatus) at its northern range edge: implications for conservation. Conserv Genet 16, 889–899 (2015). https://doi.org/10.1007/s10592-015-0708-2
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DOI: https://doi.org/10.1007/s10592-015-0708-2