Canadian Forest Service Publications
The genetic signature of rapid range expansions: How dispersal, growth and invasion speed impact heterozygosity and allele surfing. 2014. Goodsman, D.W.; Cooke, B.; Coltman, D.W.; Lewis, M.A. Theoretical Population Biology 98(2014):1-10.
Issued by: Northern Forestry Centre
Catalog ID: 35908
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As researchers collect spatiotemporal population and genetic data in tandem, models that connect demography and dispersal to genetics are increasingly relevant. The dominant spatiotemporal model of invasion genetics is the stepping-stone model which represents a gradual range expansion in which individuals jump to uncolonized locations one step at a time. However, many range expansions occur quickly as individuals disperse far from currently colonized regions. For these types of expansion, stepping-stone models are inappropriate. To more accurately reflect wider dispersal in many organisms, we created kernel-based models of invasion genetics based on integrodifference equations. Classic theory relating to integrodifference equations suggests that the speed of range expansions is a function of population growth and dispersal. In our simulations, populations that expanded at the same speed but with spread rates driven by dispersal retained more heterozygosity along axes of expansion than range expansions with rates of spread that were driven primarily by population growth. To investigate surfing we introduced mutant alleles in wave fronts of simulated range expansions. In our models based on random mating, surfing alleles remained at relatively low frequencies and surfed less often compared to previous results based on stepping-stone simulations with asexual reproduction.
Plain Language Summary
The genetic variation in populations of animals that only travel short distances has been well studied. The dominant models to explain the genetics in these populations are stepping-stone models, in which individuals jump to uncolonized locations one step at a time. These models may not apply in the case of animals that disperse far from currently colonized regions, such as forest insects, so we developed a mathematical model of the genetic diversity patterns of populations of an invasive species subject to long-range dispersal. The model predicted that such populations would gradually lose genetic variation over time and space. Populations that were expanding primarily through dispersal would be expected to retain genetic diversity longer than populations that were expanding primarily through population growth. Additional findings from this study indicate that models that are well suited to species with short-range dispersal may not be well suited to species with long-range dispersal such as forest insects.