Allele frequencies and selection coefficients in locally adapted populations

Area of Science:

• Evolutionary biology
• Population genetics
• Ecological genomics

Background:

• Accurate estimation of natural selection strength at the genetic level is crucial for understanding evolutionary change.
• Populations in migration-selection balance offer a tractable system for studying selection on locally adaptive alleles.
• High FST values at specific genetic loci can indicate alleles selected differently across populations.

Purpose of the Study:

• To develop and validate methods for quantifying the strength of selection on locally adaptive alleles in migration-selection balance.
• To analyze the relationship between selection coefficients, allele frequencies, migration rates, and population structure.
• To provide a practical tool for researchers studying adaptation in natural populations.

Main Methods:

• Analysis of a 1-locus, 2-allele model under migration-selection balance.
• Simulations comparing finite and infinite population models.
• Derivation of theoretical relationships for infinite population models.
• Development of an Excel spreadsheet for calculating selection coefficients and standard errors.

Main Results:

• Finite and infinite population models yield similar results for migration-selection balance.
• Selection coefficients are dependent on equilibrium allele frequencies, migration rates, dominance, and relative population sizes.
• FST values are directly related to the selection coefficients acting on alleles.
• A method and tool are provided to calculate selection coefficients from population parameters.

Conclusions:

• The developed methods enable quantification of selection on locally adaptive alleles in migration-selection balance.
• This work provides a valuable tool for ecological genomics and the study of adaptation.
• Understanding selection strength is essential for interpreting genetic variation in natural populations.