Beginning in Generation 1 [not shown] with 50 populations all with N = 10 and  f(B) = q = 0.5, random drift across populations produces a normal distribution with a mean of q = 0.5 in Generation 2. In successive generations, drift of q within populations increases the variance of q among populations. In Generation 5, one population has become fixed for B (q = 1.0), and starting in Generation 8, one population has lost allele B (q = 0.0). The distribution of q across populations is roughly flat by Generation 10, and is strongly U-shaped by Generation 20. Fixation and loss are "absorbing barriers": once allelic diversity in a population has been lost, it cannot be regained. In this simulation, about 30% of the populations have each lost or fixed allele B by Generation 20.

    HOMEWORK: Repeat this simulation with the MatLab program WriFish.m with 50 populations of N = 10 @ for 20 generations. Compare that display with the one here. Can you see the same pattern of a U-shaped distribution.