Populations often adapt to spatially heterogeneous environments via substitutions or allele frequency changes at many loci spread across the genome. Subsequent contact between diverged populations can produce unfit hybrids, which inhibits genetic exchange across the genome, thus setting the stage for further divergence and speciation. How such polygenic divergence builds up or is maintained depends on the coupled dynamics of multiple loci under selection, making it challenging to predict. In this talk, I will outline simple theoretical approximations based on effective migration rates that capture how coupling or linkage disequilibria (LD) between loci influences the maintenance of polygenic adaptive divergence. This analysis allow us to clarify how genetic architecture (i.e., the numbers, selective and dominance effects and linkage relationships of selected variants) influences divergence in the face of gene flow and genetic drift. I will conclude my talk with a broader perspective on...
In a simple, constant environment does evolution continue forever? Does extensive diversification via small genetic and ecological differences? What are general evolutionary consequences of organismic complexity? Hints from long term laboratory evolution experiments and from genomic data of within-species bacterial diversity motivate considering these questions. Several simple models of evolution with small ecological feedback will be introduced, with the high dimensionality of phenotype space enabling mathematical analysis.
