Preprint develops population genetic theory for how bottlenecks shape mean fitness and inbreeding depression

A preprint on bioRxiv presents a theoretical population genetics analysis examining the consequences of sudden reductions in population size — so-called bottleneck events — for mean fitness and inbreeding depression. When a population is dramatically reduced, the rate of genetic drift increases, reducing genetic variability and raising average homozygosity. This increased homozygosity exposes recessive or partially recessive deleterious alleles to natural selection, which may lead to their purging from the population.

The authors develop formal theory to describe the dynamics of this process, including the conditions under which mean fitness might ultimately recover after an initial post-bottleneck decline, and how inbreeding depression is expected to change as deleterious variation is either purged or retained depending on the severity and duration of the bottleneck.

The work is relevant to conservation genetics — where small or fragmented wildlife populations are often subject to bottleneck effects — and to plant and animal breeding programmes, where controlled inbreeding and bottlenecks are used deliberately. It is also of theoretical interest to evolutionary geneticists concerned with the maintenance of genetic load in natural populations.

This is a preprint and has not yet undergone peer review. The analysis is primarily mathematical and will be most directly accessible to researchers with a background in quantitative or population genetics.