Figure 2. The stepping-stone model for all hybrid zones, and the parameters used. Two non-admixed infinite size populations flank 19 admixed demes (i.e. H1, H2, …, H19). At generation 1 each admixed deme has an ancestry proportion p of individuals from population 2. Individuals symmetrically migrate with a migration rate ofm to adjacent admixed demes, but not back into source populations. We modeled 12 different hybrids zones, each with a combination of deme size N (100, 500,1000), migration rate m(0.1, 0.01), and selection type (No Selection, Directional and Underdominance, BDM incompatibility). We sampled 30 individuals and genotyped the same 110 markers on the 100thgeneration, and again in the 1000th generation. We replicated this process 100 times.