Figure P18.6. Evolution of a chromosomal arrangement in two demes, under gene flow and selection against heterozygotes. Allele frequencies in two demes (p₁, p₂) are plotted on the two axes, with the population starting at various points. (Red) Unstable equilibria; (blue) stable equilibria. The left panel is for M = m/s = 0.15. There are two stable equilibria with different arrangements common in different demes (top left, bottom right), separated by an unstable equilibrium at p₁ = p₂ = 1/2. The right panel is for a higher rate of gene flow (M = m/s = 0.2). Now, the two asymmetrical equilibria exist, but are unstable (red dots at top left, bottom right): One or the other arrangement will fix in both demes.

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