Polygenic Adaptation to an Environmental Shift: Temporal Dynamics of Variation Under Gaussian Stabilizing Selection...

Area of Science:

• Evolutionary genetics
• Population genetics

Background:

• Models of natural selection often assume rapid fixation of beneficial mutations.
• Selection strength decreases as populations adapt to new trait optima.

Purpose of the Study:

• Investigate hitchhiking patterns during adaptation to an optimum shift.
• Examine factors influencing sweep dynamics and fixation times.

Main Methods:

• Explicit forward simulations of a single trait with additive-effect mutations.
• Simulated adaptation to an "optimum shift" scenario.

Main Results:

• Hitchhiking patterns are detectable only with large optimum shifts, low mutation rates to large-effect mutations, and rapid fixation.
• Partial sweeps have minimal impact on linked variation; populations often reach the optimum before sweeps complete.
• Mutational variance influences hitchhiking magnitude, while effect size distribution has minor impact on adaptation time.

Conclusions:

• Adaptation to optimum shifts results in longer fixation times than standard directional selection models.
• Declining selection and interference among sites contribute to extended fixation times.