The genomics of ecological vicariance in threespine stickleback fish
Friday seminar by Marius Roesti from University of Basel (Switzerland) and University of British Columbia (Canada)
Populations occurring in similar habitats and displaying similar phenotypes are increasingly used to explore to what extent organisms re-use the same genomic loci to repeatedly solve an ecological challenge. As an alternative to such parallel evolution, a recurrent phenotype-habitat association across multiple populations may trace back to the fragmentation of a single ancestral population, followed by genetic exchange with ecologically different populations. I will evaluate these alternatives by presenting recent work based on dense genome-wide polymorphism data from threespine stickleback fish residing in multiple streams and a large adjoining lake in Central Europe. Demographic reconstructions as well as genomically widespread and localized patterns of genetic divergence, diversity and linkage reveal an unexpected selective and demographic history. Overall, the results highlight how the colonization background, natural selection and gene flow interact to shape population divergence, and caution against conclusions about genomic parallelism in the absence of robust information on the evolutionary history of divergent populations.
Marius Roesti, PhD
University of Basel (Switzerland) and University of British Columbia (Canada)