How Obstacles Perturb Population Fronts and Alter Their Genetic Structure

Area of Science:

• Ecology
• Evolutionary Biology
• Population Genetics

Background:

• Environmental heterogeneity influences population spread and genetic makeup.
• Isolated obstacles are key components of heterogeneous environments.
• Understanding range expansions is crucial for predicting population dynamics.

Purpose of the Study:

• To investigate the impact of isolated obstacles on population front shape and genetic composition.
• To quantify the effects of obstacles on genetic drift during range expansions.
• To introduce and explain the concept of 'geometry-enhanced genetic drift'.

Main Methods:

• Experimental population expansion using bacteriophage T7 on Escherichia coli lawns.
• Quantitative analysis of population front dynamics using inkjet-printed lawns.
• Theoretical modeling including constant speed and reaction-diffusion models, complemented by stochastic simulations.

Main Results:

• Isolated obstacles create persistent, long-lived distortions (kinks) in the population front, irrespective of obstacle shape.
• Obstacles amplify genetic drift, leading to increased abundance of frontier genotypes near the obstacle ('geometry-enhanced genetic drift').
• The effects of obstacles on population genealogy were characterized and rationalized through modeling.

Conclusions:

• Isolated obstacles significantly alter population front dynamics and genetic structure during range expansions.
• Geometry-enhanced genetic drift is a novel mechanism influencing genetic composition at expanding frontiers.
• These findings provide insights into population dynamics in complex, heterogeneous environments.