The effect of selection on the standardized variance of gene frequency.

The effect of directional and heterotic selection on the standardized variance of gene frequency (f=σ q (2) /¯q(1-¯q)) has been examined. It has been found that heterotic selection always results in f values lower than those expected due to drift alone. Additive directional selection can result in low f values, but values larger than those expected due to drift will be observed under additive selection with low initial gene frequency, or when the populations have been separated for a very long period of time in which case f expected due to drift is quite high (around 0.7 or greater). The effect of selection on f is unlikely to be detected if the observed value of f is less than 0.1.