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 100^thgeneration, and again in the 1000^th generation. We replicated this process 100 times.