Allele surfing promotes microbial adaptation from standing variation

Area of Science:

• Evolutionary biology
• Microbial ecology
• Population genetics

Background:

• Range expansions facilitate the establishment and high-frequency fixation of mutations at expanding margins.
• Allele surfing, a key mechanism in range expansions, has been implicated in significant genetic changes within species, particularly microbial communities.
• The precise conditions under which allele surfing influences adaptation (promoting or hindering) remain incompletely understood.

Discussion:

• This study demonstrates that range expansions, coupled with standing adaptive variation, significantly increase mean fitness compared to spatially uniform expansions.
• The observed adaptation gains are attributed to 'soft' selective sweeps initiated by surfing beneficial mutations.
• The frequency of these surfing events is highly sensitive to the strength of genetic drift, which is influenced by strain-specific and environmental factors.

Key Insights:

• Range expansions with standing adaptive variation lead to greater fitness increases than uniform population expansions.
• Soft selective sweeps, driven by allele surfing, are a primary mechanism for enhanced adaptation.
• Genetic drift's strength critically modulates the rate of allele surfing events.

Outlook:

• Allele surfing enhances the rate of adaptation relative to biomass production.
• This mechanism could be crucial for the development of biofilms and other resource-limited populations facing environmental pressures.
• Further research can explore optimizing conditions for allele surfing to aid adaptation in challenging ecosystems.