Demographic feedbacks can hamper the spatial spread of a gene drive

TL;DR

This study investigates how demographic feedbacks influence the spatial invasion of gene drives, revealing that population dynamics can hinder or reverse gene drive spread, which is crucial for understanding their real-world effectiveness.

Contribution

It introduces a reaction-diffusion model incorporating demographic feedbacks, providing new insights into the conditions affecting gene drive invasion success.

Findings

Demographic feedbacks can reverse the direction of gene drive invasion.

Population dynamics are crucial in predicting gene drive spread.

Numerical simulations support the analytical predictions.

Abstract

This paper is concerned with a reaction--diffusion system modeling the fixation and the invasion in a population of a gene drive (an allele biasing inheritance, increasing its own transmission to offspring). In our model, the gene drive has a negative effect on the fitness of individuals carrying it, and is therefore susceptible of decreasing the total carrying capacity of the population locally in space. This tends to generate an opposing demographic advection that the gene drive has to overcome in order to invade. While previous reaction--diffusion models neglected this aspect, here we focus on it and try to predict the sign of the traveling wave speed. It turns out to be an analytical challenge, only partial results being within reach, and we complete our theoretical analysis by numerical simulations. Our results indicate that taking into account the interplay between population dynamics and population genetics might actually be crucial, as it can effectively reverse the direction of the invasion and lead to failure. Our findings can be extended to other bistable systems, such as the spread of cytoplasmic incompatibilities caused by Wolbachia.