Expected F_ST values for 2,000 generations of simulated neutral divergence. (A) During divergence without gene flow (m = 0) F_ST rapidly increases, achieving fixation at 2,000 generations under all recombination rates; (B) During divergence with low levels of migration (m = 0.0001) F_ST increases rapidly, approaching fixation at 2,000 generations for all recombination rates; (C) During divergence with intermediate levels of migration (m = 0.001) F_ST increases rapidly during the initial ∼300 generations, after which it continues to fluctuate around 0.2 with some variation between recombination rates; and (D) During divergence with high levels of gene flow (m = 0.01) low levels of F_ST are maintained across all 2,000 generations of divergence.