Genetic drift at expanding frontiers promotes gene segregation

Competition between random genetic drift and natural selection play a central role in evolution: Whereas nonbeneficial 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…

• NS
  National Science Foundation

  Award: 0654191
• HU
  Harvard University
• DF
  Deutsche Forschungsgemeinschaft
• MR
  Materials Research Science and Engineering Center, Harvard University
• NI
  National Institute of General Medical Sciences
• DO
  Division of Materials Research