Population genetic structure of the round goby in Lake Michigan: implications for dispersal of invasive species
Understanding subsequent dispersal of non-native species following introduction is important for predicting the extent and speed of range expansion and is critical for effective management and risk assessment. Post-introduction dispersal may occur naturally or via human transport, but assessing the relative contribution of each is difficult for many organisms. Here, we use data from seven microsatellite markers to study patterns of dispersal and gene flow among 12 pierhead populations of the round goby (Neogobius melanostomus) in Lake Michigan. We find significant population structure among sampling sites within this single Great Lake: (1) numerous populations exhibited significant pairwise F ST and (2) a Bayesian assignment analysis revealed three distinct genetic clusters, corresponding to different pierhead locations, and genetic admixture between these clusters in the remaining populations. Genetic differentiation (F ST) is generally related to geographic distance (i.e., isolation by distance), but is periodically interrupted at the scale of Lake Michigan due to gene flow among geographically distant sites. Moreover, average genetic differentiation among populations exhibit a significant, negative correlation with the amount of shipping cargo at ports. Our results, therefore, provide evidence that genetic structure of the round goby in Lake Michigan results from limited natural dispersal with frequent long-distance dispersal through anthropogenic activities such as commercial shipping. Our study suggests that while round gobies can undoubtedly disperse and found new populations through natural dispersal mechanisms, their spread within and among the Great Lakes is likely aided by transport via ships. We, therefore, recommend that ballast-water treatment and management may limit the spread of non-native species within the Great Lakes after the initial introduction in addition to preventing the introduction of non-native species to the Great Lakes.
KeywordsGreat Lakes Neogobius melanostomus Ballast water Fish movement Aquatic invasive species Gene flow
We thank Dustin Wcisel for help in the laboratory and with sampling and Tyler Armstrong for help with the 2008 pilot study. Jeff LaRue, Jordan Allison, Amanda Potter, and Sarah LaRue provided sampling assistance. Yakuta Bhagat, Mark Luttenton, and two anonymous reviewers provided helpful comments on this manuscript. Funding for this project was provided by Grand Valley State University’s Student Summer Scholars program and the Bill and Diana Wipperfurth Student Research Scholarship.
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