The selection limit due to the conflict between truncation and stabilizing selection with mutation

Area of Science:

• Evolutionary genetics
• Quantitative genetics
• Population genetics

Background:

• Long-term selection response can be limited by declining genetic variance or selection differential.
• Understanding these limitations is crucial for predicting evolutionary trajectories.

Purpose of the Study:

• To model the conflict between truncation and stabilizing selection.
• To analyze the reduction in selection differential and its impact on genetic variation.
• To investigate the maintenance of genetic variation under mutation-selection balance.

Main Methods:

• Analysis of a model with truncation and stabilizing selection in an infinite population.
• Assumption of a normal phenotypic distribution.
• Application of the "House-of-cards" approximation for mutation-selection balance.

Main Results:

• The limit to selection is a function of truncation intensity (kappa), stabilizing selection intensity (omega^2), and phenotypic variance (sigma^2).
• Truncation selection substantially reduces equilibrium genetic variance compared to stabilizing selection alone.
• The proportional reduction in variance is greatest under weak selection and plateaus with strong truncation selection.

Conclusions:

• Mutation-selection balance alone may not account for the high genetic variation observed in long-term selection experiments.
• The interplay between different selection types significantly impacts genetic variation dynamics.
• Further research is needed to explain high genetic variation levels in evolutionary studies.