Stabilizing selection, purifying selection, and mutational bias in finite populations

Area of Science:

• Population genetics
• Evolutionary genomics

Background:

• Genomic traits like codon usage and noncoding sequence lengths may be shaped by stabilizing selection.
• Mutations affecting these traits often exhibit directional bias.

Purpose of the Study:

• Investigate the impact of mutational bias on genomic traits under stabilizing selection in finite populations.
• Examine the relationship between selection intensity, population size, and mutational bias.

Main Methods:

• Employed two distinct mutational models.
• Utilized a matrix method for variant frequency distribution and Monte Carlo simulations.
• Derived analytical approximations for theoretical insights.

Main Results:

• The scaled intensity of selection is largely independent of effective population size.
• Selection intensity is primarily determined by the logarithm of the mutational bias parameter.
• Purifying selection with synergistic effects is sensitive to population size, contrasting with codon usage.

Conclusions:

• Distinguishing between stabilizing and purifying selection using DNA variant frequency spectra may be challenging.
• Mutational bias plays a crucial role in shaping genomic traits under stabilizing selection.
• Findings challenge previous assumptions about the population size sensitivity of purifying selection.