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arXiv · 0812.2345

Genetic drift at expanding frontiers promotes gene segregation

Oskar Hallatschek·Pascal Hersen·Sharad Ramanathan·David R. Nelson
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Abstract

Competition between random genetic drift and natural selection plays a central role in evolution: Whereas non-beneficial mutations often prevail in small populations by chance, mutations that sweep through large populations typically confer a selective advantage. Here, however, we observe chance effects during range expansions that dramatically alter the gene pool even in large microbial populations. Initially well-mixed populations of two fluorescently labeled strains of Escherichia coli develop well-defined, sector-like regions with fractal boundaries in expanding colonies. The formation of these regions is driven by random fluctuations that originate in a thin band of pioneers at the expanding frontier. A comparison of bacterial and yeast colonies (Saccharomyces cerevisiae) suggests that this large-scale genetic sectoring is a generic phenomenon that may provide a detectable footprint of past range expansions.

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Oskar Hallatschek, Pascal Hersen, Sharad Ramanathan, David R. Nelson. 2008-12-12. Genetic drift at expanding frontiers promotes gene segregation. https://doi.org/10.1073/pnas.0710150104

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