Evolution of populations expanding on curved surfaces

TL;DR

This study explores how curved surfaces influence the genetic diversity and evolutionary dynamics of expanding populations, revealing significant effects of surface geometry on genetic variation and descendant success.

Contribution

It introduces a combined simulation and analytical approach to understand population expansion on curved surfaces, highlighting the impact of surface features on genetic diversity and lineage success.

Findings

Genetic diversity transiently increases then decreases at the population front.

Individuals near bumps have higher expected descendants.

Surface geometry significantly affects evolutionary outcomes.

Abstract

The expansion of a population into new habitat is a transient process that leaves its footprints in the genetic composition of the expanding population. How the structure of the environment shapes the population front and the evolutionary dynamics during such a range expansion is little understood. Here, we investigate the evolutionary dynamics of populations consisting of many selectively neutral genotypes expanding on curved surfaces. Using a combination of individual-based off-lattice simulations, geometrical arguments, and lattice-based stepping-stone simulations, we characterise the effect of individual bumps on an otherwise flat surface. Compared to the case of a range expansion on a flat surface, we observe a transient relative increase, followed by a decrease, in neutral genetic diversity at the population front. In addition, we find that individuals at the sides of the bump have a dramatically increased expected number of descendants, while their neighbours closer to the bump's centre are far less lucky. Both observations can be explained using an analytical description of straight paths (geodesics) on the curved surface. Complementing previous studies of heterogeneous flat environments, the findings here build our understanding of how complex environments shape the evolutionary dynamics of expanding populations.