The gene's-eye view of quantitative genetics

TL;DR

This paper develops a gene-centric model of quantitative trait evolution, linking allelic frequency dynamics at many loci to trait distribution changes using advanced stochastic methods.

Contribution

It introduces a finite-loci model with selection, drift, recombination, and mutation, analyzing the limit as loci become infinite under strong recombination.

Findings

Loci become independent in the infinite limit under certain conditions.

Explicit stationary distribution for allelic frequencies derived.

Model connects gene-level dynamics to trait evolution in a rigorous way.

Abstract

Modelling the evolution of a continuous trait in a biological population is one of the oldest problems in evolutionary biology, which led to the birth of quantitative genetics. With the recent development of GWAS methods, it has become essential to link the evolution of the trait distribution to the underlying evolution of allelic frequencies at many loci, co-contributing to the trait value. The way most articles go about this is to make assumptions on the trait distribution, and use Wright's formula to model how the evolution of the trait translates on each individual locus. Here, we take a gene's eye-view of the system, starting from an explicit finite-loci model with selection, drift, recombination and mutation, in which the trait value is a direct product of the genome. We let the number of loci go to infinity under the assumption of strong recombination, and characterize the limit behavior of a given locus with a McKean-Vlasov SDE and the corresponding Fokker-Planck IPDE. In words, the selection on a typical locus depends on the mean behaviour of the other loci which can be approximated with the law of the focal locus. Results include the independence of two loci and explicit stationary distribution for allelic frequencies at a given locus (under some assumptions on the fitness function).