RESEARCH ARTICLE Genetic structure and diversity of spotted gar (Lepisosteus oculatus) at its northern range edge: implications for conservation William R. Glass • Ryan P. Walter • Daniel D. Heath • Nicholas E. Mandrak • Lynda D. Corkum Received: 10 November 2014 / Accepted: 27 February 2015 Ó Springer Science+Business Media Dordrecht 2015 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 sam- ples, 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 ana- lyses. 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 subpopula- tions is very low, ranging from essentially complete iso- lation 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 differen- tiation for those populations and provide a source of ge- netic 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 di- versity of this species. Additionally, the asymmetrical ge- netic connectivity among the Point Pelee and Rondeau Bay sites highlights the sensitivity of Point Pelee to environ- mental perturbation and habitat degradation. Keywords Spotted gar Á Microsatellite Á Edge population Á Genetic structure Introduction Conservation strategies for species at risk aim to consider range-wide genetic variation and diversity (e.g. Reed and Frankham 2003) and attempt to afford protection not only at the species level, but also to include genetically distinct populations (Jelks et al. 2008). In contrast to core populations, populations at the edge of a species’ range may display disproportionately higher genetic variation (Munwes et al. 2010) as edge populations tend to be more isolated, exhibit smaller population sizes, and experience increased levels of genetic drift and differentiation (Garcia- Ramos and Kirkpatrick 1997). The detection of genetic diversity within a species, including the identification of Electronic supplementary material The online version of this article (doi:10.1007/s10592-015-0708-2) contains supplementary material, which is available to authorized users. W. R. Glass (&) Á L. D. Corkum Department of Biology, University of Windsor, Windsor, ON N9B 3P4, Canada e-mail: William.glass@dfo-mpo.gc.ca; glass@uwindsor.ca Present Address: W. R. Glass Á R. P. Walter Á N. E. Mandrak Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada, Burlington, ON L7R 4A6, Canada R. P. Walter Á D. D. Heath Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON N9B 3P4, Canada Present Address: N. E. Mandrak Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada 123 Conserv Genet DOI 10.1007/s10592-015-0708-2