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The solitary wave of asexual evolution
Igor M Rouzine1, John Wakeley, John M Coffin
1Department of Molecular Biology and Microbiology, Tufts University, Boston, MA 02111, USA. irouzine@tufts.edu
Summary
This study introduces a new model to predict mutation accumulation in asexual populations. Linkage slows beneficial mutation acquisition, supporting the Fisher-Muller hypothesis on evolutionary progression.
Area of Science:
- Evolutionary biology
- Population genetics
- Molecular evolution
Background:
- Understanding mutation accumulation is key to predicting evolutionary trajectories.
- Previous models often simplify the complex interplay of mutation, selection, and linkage.
Purpose of the Study:
- To develop an analytic model predicting mutation accumulation (advantageous vs. deleterious) in asexual populations.
- To investigate the impact of linked loci on mutation accumulation rates.
- To explain observed fitness-population size relationships in viruses.
Main Methods:
- Developed a novel analytic model for linked, identical loci with low selection coefficients.
- Incorporated back and compensating mutations.
- Validated model predictions using Monte Carlo simulations across various population sizes.
Main Results:
- The model accurately predicts mutation accumulation rates for nearly all population sizes.
- Linkage significantly slows the accumulation of advantageous mutations in a broad range of population sizes.
- The distribution of sequences evolves as a traveling wave, with speed and width dependent on population size and other parameters.
Conclusions:
- The developed model provides a comprehensive framework for understanding mutation dynamics in asexual populations.
- Linkage between loci hinders progressive evolution, supporting the Fisher-Muller hypothesis.
- The model explains the logarithmic fitness-population size dependence observed in RNA viruses.