On the relationship between the load and the variance of relative fitness

BACKGROUND: Operation of natural selection can be characterized by a variety of quantities. Among them, variance of relative fitness V and load L are the most fundamental. RESULTS: Among all modes of selection that produce a particular value V of the variance of relative fitness, the minimal value L(min )of load L is produced by a mode under which fitness takes only two values, 0 and some positive value, and is equal to V/(1+V). CONCLUSIONS: Although it is impossible to deduce the load from knowledge of the variance of relative fitness alone, it is possible to determine the minimal load consistent with a particular variance of relative fitness. The concept of minimal load consistent with a particular biological phenomenon may be applicable to studying several aspects of natural selection. REVIEWERS: The manuscript was reviewed by Sergei Maslov, Alexander Gordon, and Eugene Koonin.