stabilizing selection & compensatory evolution
Fierst JL & Hansen TF 2010 Genetic architecture and postzygotic reproductive isolation: evolution of Bateson-Dobzhansky-Muller incompatibilities in a polygenic system. Evolution 64:675-693.
- reproductive isolation under stabilizing selection should be a plausible scenario
- to accelerate the simulations we fixed those parameters at number of loci = 20 and number of generations = 106
- μ = 0.01 mutations/locus/generation
- σm = 0.01
- the run time for these simulations was very long
- to adequately sample the parameter space and replicate our results we used extremely high per locus mutation rates
- stabilizing selection acting on a phenotypic trait with a polygenic architecture will generate a network of high-fitness genotypes on which quasi-neutral drift may take place
- separated populations may experience identical selection regimes and still drift to different positions in the network
- this may produce low-fitness hybrids
- the F1 hybrid load developed under intermediate strengths of epistasis that were strong enough to shift the hybrid phenotype away from the parental mean, but not strong enough to prevent allelic divergence
- strong trait epistasis, however, prevents genetic divergence and thus limits the evolution of reproductive isolation
- evolution along fitness isoclines, as in Figure 1, is not purely neutral
- epistatic interactions produce distinct equilibrium points that are generated by canalizing selection
- when epistasis is strong, canalizing selection overcomes drift
