A simulation study of truncation selection for a quantitative trait opposed by natural selection

Area of Science:

• Population genetics
• Quantitative genetics
• Evolutionary biology

Background:

• Understanding the interplay between artificial and natural selection is crucial for predicting evolutionary trajectories.
• Quantitative traits controlled by single loci with two alleles provide a simplified model to study complex selection dynamics.

Purpose of the Study:

• To investigate the selection response and limits of a quantitative trait under artificial selection opposing three modes of natural selection.
• To compare deterministic simulation results with empirical selection experiments.

Main Methods:

• A deterministic simulation model was employed for a large random-mating population.
• The model incorporated artificial (mass) selection against three natural selection modes: directional, overdominance, and underdominance.
• Key parameters included initial gene frequency, selection intensity, gene effect relative to environmental variation, and fitness values.

Main Results:

• The selection process duration (20-100 generations) was largely independent of the natural selection mode.
• Observed outcomes included fixation of the artificially selected allele, stable or unstable equilibria, and loss of the favored allele.
• The specific outcome was contingent upon parameter values such as initial gene frequency and selection intensity.

Conclusions:

• The dynamics of allele frequency change are highly sensitive to the balance between artificial and natural selection pressures.
• Deterministic simulations provide a valuable tool for exploring evolutionary processes and can predict outcomes observed in experimental evolution.
• Parameter values critically determine whether selection leads to fixation, equilibrium, or allele loss.