Figure 7. A schematic partition of a broad distribution of fitness effects.

Sufficiently weakly selected mutations are described by the infinitesimal limit analyzed here, with an effective selection coefficient given by the mean squared fitness effect. Those with sufficiently strong selection coefficients generate a reduction in the effective population size according to the harmonic mean. The boundaries between these two regimes (and the width of the intermediate zone separating them) are determined self consistently by the emergent genealogical process, and vary as a function of the underlying parameters.