Natural selection of mutants that modify population structure

TL;DR

This paper explores how changes in population structure, specifically dispersal networks, influence the success of mutants with equal reproductive rates, revealing that increased motility generally boosts invasion chances but with notable exceptions.

Contribution

It introduces a framework analyzing how mutants with identical fitness but different dispersal structures affect evolutionary outcomes, highlighting the role of population connectivity.

Findings

Enhanced motility generally increases fixation probability.

The layout of dispersal links critically influences invasion success.

In lattice populations, motility effects are comparable to fitness changes.

Abstract

Evolution occurs in populations of reproducing individuals. It is well known that population structure can affect evolutionary dynamics. Traditionally, natural selection is studied between mutants that differ in reproductive rate, but are subject to the same population structure. Here we study how natural selection acts on mutants that have the same reproductive rate, but experience different population structures. In our framework, mutation alters population structure, which is given by a graph that specifies the dispersal of offspring. Reproduction can be either genetic or cultural. Competing mutants disperse their offspring on different graphs. A more connected graph implies higher motility. We show that enhanced motility tends to increase an invader's fixation probability, but there are interesting exceptions. For island models, we show that the magnitude of the effect depends crucially on the exact layout of the additional links. Finally, we show that for low-dimensional lattices, the effect of altered motility is comparable to that of altered fitness: in the limit of large population size, the invader's fixation probability is either constant or exponentially small, depending on whether it is more or less motile than the resident.