Stabilizing selection, mutational bias, and the evolution of sex

Area of Science:

• Evolutionary Biology
• Population Genetics

Background:

• Stabilizing selection favors a fixed phenotypic optimum.
• Asexual reproduction is often predicted to be advantageous under stabilizing selection due to efficient maintenance of optimal gene combinations.
• This prediction assumes unbiased mutation effects on phenotypes.

Purpose of the Study:

• To investigate the impact of mutational bias on the evolution of sexual reproduction under stabilizing selection.
• To determine if mutational bias can favor sex despite stabilizing selection.
• To model polygenic traits affected by mutation, drift, and selection.

Main Methods:

• Developed a theoretical model of stabilizing selection on multiple polygenic traits.
• Incorporated mutational bias and its effects on population mean phenotype.
• Utilized individual-based simulations and quasi-linear expectation (QLE) approximations.

Main Results:

• Mutational bias significantly reduces the mean fitness of asexual populations compared to sexual ones, especially with weak to moderate mutation effects.
• Mutation and genetic drift together drive asexual populations away from the phenotypic optimum.
• Positive rates of sex are favored when mutational bias is present; populations evolve towards asexuality without bias.

Conclusions:

• Mutational bias is a critical factor that can reverse the expected advantage of asexuality under stabilizing selection.
• The interplay of mutation, drift, and selection determines the optimal reproductive strategy.
• Understanding mutational bias is essential for explaining the maintenance of sex in natural populations.