Figure 1. Fixation probability as a function of the position where the mutant is introduced (for , and ).

The wildtype wave profile (arbitrarily rescaled) is shown by the dashed line. The probability profile virtually vanishes in the bulk of the wave, but suddenly rises at a characteristic distance from the front, and then saturates. The shape of the function is characterized by , defined as the distance between the two points at which the curves reach half of their saturation values, by the characteristic width over which the curve rises, and by its saturation height .