Figure 1.

Schematic of the expansion models studied. Each square corresponds to a subpopulation, with gray borders indicating subpopulations not colonized at a time step. Each time step, a new deme is colonized (black, dashed arrows), and other demes undergo neutral genetic drift (gray arrows). We compare the allele frequencies {X_t} at the expansion origin d₀ (dashed borders) with the allele frequencies {${\tilde{X}}_t$} at the expansion front (shaded backgrounds).