Figure 3. Divergence process between Arabidopsis lyrata, A. halleri and A. thaliana at unlinked genes (genomic background) and trans-specifically shared pairs of S-alleles.

Divergence times were taken from Koch et al. [18],[58]. θ_lyrata, θ_halleri and θ_A, refer to polymorphism (θ = 4Nμ· in A. lyrata, A. halleri and their common ancestor. As compared to unlinked genes, divergence between trans-specifically shared S-alleles is affected by two confounding factors: (1) lower effective population size than the genomic background reducing coalescence time in the ancestral species, and (2) expected higher introgression as represented by thicker dark grey arrows.