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Asynchronous abundance fluctuations can drive giant genotype frequency fluctuations
Joao A Ascensao1,2, Kristen Lok1,3, Oskar Hallatschek4,5,6
1Department of Bioengineering, University of California Berkeley, Berkeley, CA, USA.
Biorxiv : the Preprint Server for Biology
|April 2, 2024
Summary
Large population fluctuations can unexpectedly alter genetic frequencies due to asynchronous responses between genotypes. This study reveals chaotic dynamics driving these changes, impacting evolution beyond genetic drift.
Area of Science:
- Ecology
- Evolutionary Biology
- Microbiology
Background:
- Stochastic population abundance fluctuations are common in nature.
- These fluctuations were previously thought to have minimal impact on evolution.
- The assumption was that all alleles fluctuate in unison, preserving relative frequencies.
Purpose of the Study:
- To investigate if asynchronous abundance fluctuations between genotypes can drive significant changes in genotype frequencies.
- To develop a model explaining giant frequency fluctuations beyond genetic drift.
- To explore the implications of these fluctuations for eco-evolutionary dynamics.
Main Methods:
- Serial dilution of mixed *E. coli* strains to observe frequency changes.
- Development of a mathematical model for abundance and frequency fluctuations.
- Analysis of asynchronous offspring number variations between genotypes.
- Examination of mixed-genotype *S. cerevisiae* populations.
Main Results:
- Observed giant genotype frequency fluctuations exceeding genetic drift expectations.
- Demonstrated that asynchronous offspring numbers between genotypes cause these fluctuations.
- Developed a model accurately predicting abundance and frequency fluctuation scaling.
- Identified chaotic dynamics as the underlying mechanism for exponential divergence.
Conclusions:
- Asynchronous fluctuations in population abundance significantly impact evolutionary trajectories.
- Decoupling noise in offspring numbers is a key driver of these evolutionary changes.
- Such noise is likely widespread in biological populations, affecting ecological and evolutionary outcomes.
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