Investigating the effects of landscape heterogeneity and dispersal on the genetics and spread of an introduced fish, Tench (Tinca tinca), using population genomic and simulation approaches

Background/Question/Methods

As the ecological and socio-economic damages of invasive species rise worldwide, understanding the consequences of dispersal on their geographic spread and evolution is critical. When long-distance dispersal events are rare, the number of individuals colonizing new habitats is generally small; thus, heightened drift on the leading edge is expected to result in genetic diversity losses as the population expands through space. Furthermore, mechanisms favouring the accumulation of fast dispersers on the invasion fronts are expected to accelerate the expansion and lead to the disproportionate loss of slow dispersers’ alleles on the leading edge. To investigate mechanisms driving changes in genetic diversity and expansion rate, we used two complementary approaches. First, we used population genomic approaches to examine patterns of genetic diversity resulting from the rapid expansion of an introduced Tench (Tinca tinca) population in eastern North America. Second, we used an individual-based spatially explicit simulation model to explore the effects of dispersal ability, heritability, and gaps in suitable habitat on genetic diversity and spread rate using the Tench population as a model.

Results/Conclusions

Our genomic data revealed that the expanding population did not exhibit severe losses of genetic diversity from the core to the invasion fronts. Furthermore, the direction and magnitude of genetic diversity changes varied between the two invasion fronts. The simulation then highlighted that increased dispersal ability, its heritability, and landscape patchiness, not only favored faster range expansions and mitigated losses in genetic diversity, but also increased variability in the outcomes of range expansion among the invasion fronts. As different mechanisms led to similar outcomes in range expansion rate and genetic diversity changes, experiments testing dispersal traits across the invaded range would be particularly well suited to test the eco-evolutionary predictions of our model for Tench and improve predictions of the evolutionary trajectory of the invasion.