Population Genetics with Fluctuating Population Sizes

TL;DR

This paper reviews an alternative population genetics model that incorporates fluctuating population sizes, revealing how such fluctuations can influence species fixation and challenge the assumptions of fixed-size models.

Contribution

It introduces a model allowing independent population size fluctuations and demonstrates their impact on fixation dynamics near equilibrium.

Findings

Fluctuations can induce selection even when species are neutral at equilibrium.

Standard fixed-size models are incomplete in capturing real population dynamics.

Timescale separation enables analysis of fluctuations-induced effects.

Abstract

Standard neutral population genetics theory with a strictly fixed population size has important limitations. An alternative model that allows independently fluctuating population sizes and reproduces the standard neutral evolution is reviewed. We then study a situation such that the competing species are neutral at the equilibrium population size but population size fluctuations nevertheless favor fixation of one species over the other. In this case, a separation of timescales emerges naturally and allows adiabatic elimination of a fast population size variable to deduce the fluctuations-induced selection dynamics near the equilibrium population size. The results highlight the incompleteness of the standard population genetics with a strictly fixed population size.