Isolation-by-Distance and Outbreeding Depression Are Sufficient to Drive Parapatric Speciation in the Absence of Environmental Influences
Figure 1
Histograms of Gene Flow Distances.
Shown are histograms of the distances traveled, measured as simple Euclidean distance from grid cell center to grid cell center, for all chromosomes in the population within a single representative generation (step 200,000). Three typical simulations were conducted under the following selected simulation parameters: (A) movement distance δ = 1.5, outbreeding depression threshold θ = 0.6; (B) movement distance δ = 1.5, outbreeding depression disabled (θ = +∞); (C) movement distance δ = 5, outbreeding depression threshold θ = 0.6. For all graphs, target population size was 128,000, and grid size was 400×400. The movement distance parameter δ roughly defines the mean distance traveled by individuals in each of three phases within a generation (migration, mate selection, and offspring placement), so the net dispersal distance over a generation was usually greater than δ itself.