Effective fitness under fluctuating selection with genetic drift

The natural environment fluctuates for virtually every population of organisms. As a result, the fitness of a mutant may vary temporally. While commonly used for summarizing the effect of fluctuating selection on the mutant, geometric mean fitness can be misleading under some circumstances due to the influence of genetic drift. Here, we show by mathematical proof and computer simulation that, with genetic drift, the geometric mean fitness does not accurately reflect the overall effect of fluctuating selection. We propose an alternative measure based on the average expected allele frequency change caused by selection and demonstrate that this measure-effective fitness-better captures the overall effect of fluctuating selection in the presence of drift.

Automated summary

The natural environment fluctuates, affecting the fitness of organisms. The commonly used measure of geometric mean fitness may be misleading due to genetic drift. In this study, a new measure called effective fitness is proposed, which captures the overall effect of fluctuating selection more accurately by considering average expected allele frequency change caused by selection.