Gene surfing in expanding populations

Area of Science:

• Population genetics
• Evolutionary biology
• Theoretical ecology

Background:

• Genomic surveys aim to reconstruct migration history using neutral genetic variation.
• Understanding genetic consequences of range expansion is crucial for accurate historical reconstruction.
• Lineage fixation via 'surfing' occurs at the wave front during colonization.

Purpose of the Study:

• To study neutral gene frequency dynamics in an asexual population during one-dimensional range expansion.
• To quantify lineage fixation and genetic diversity loss at the expansion front.
• To develop analytical methods for predicting genetic consequences of range expansions.

Main Methods:

• Stochastic simulations of asexual populations undergoing range expansion.
• Analytical modeling based on reaction-diffusion systems.
• Quantification of spatial distribution of fixed lineages and heterozygosity gradients.

Main Results:

• An effective population size can be assigned to the expansion wave, controlling heterozygosity gradients.
• Cooperation ('pushed waves') results in a higher effective population size than independent proliferation ('pulled waves').
• Effective population size increases sub-linearly with deme size.

Conclusions:

• The study provides a framework for understanding genetic footprints of range expansions.
• Analytical theory accurately predicts outcomes for 'pushed waves' but needs refinement for stochastic 'pulled waves'.