Polygenic adaptation after a sudden change in environment

Area of Science:

• Evolutionary genetics
• Quantitative genetics
• Population genetics

Background:

• Polygenic adaptation, the process by which populations evolve complex traits influenced by many genes, is widespread but not well understood.
• Understanding polygenic adaptation is crucial for explaining evolutionary responses to environmental change.

Purpose of the Study:

• To analytically model the dynamics of polygenic adaptation following a sudden shift in the fitness optimum.
• To characterize the temporal phases of allele frequency changes and fixation probabilities at loci contributing to a quantitative trait.

Main Methods:

• Analytical modeling of a quantitative trait under directional and stabilizing selection.
• Characterization of allele dynamics at multiple loci contributing to phenotypic variance.

Main Results:

• Phenotypic change over time depends on the effect sizes of contributing loci.
• Identified two distinct phases in allele dynamics: a rapid directional selection phase and a slower stabilizing selection phase.
• Allele frequency differences and fixation probabilities are influenced by selection direction and magnitude.

Conclusions:

• The study provides a theoretical framework for understanding polygenic adaptation.
• Findings have implications for identifying the genetic basis of adaptation in natural populations and humans.
• The two-phase model offers insights into the tempo and mode of evolutionary genetic change.