A SIMULATION STUDY OF MULTILOCUS CLINES.

Area of Science:

• Population Genetics
• Evolutionary Biology
• Quantitative Genetics

Background:

• Fisher's method of junctions analyzes allele association in clines.
• Equilibrium models predict a "critical value" of selection for allele association.
• Previous models assumed rapid attainment of equilibrium.

Purpose of the Study:

• Investigate allele association in clines using computer simulations.
• Compare simulation results with equilibrium predictions.
• Assess the rate of approach to equilibrium under selection.

Main Methods:

• Simulated secondary contact between two infinite demes with gene flow.
• Implemented additive selection equivalent to heterozygote disadvantage on haploids.
• Utilized uniform recombination across a single chromosome.

Main Results:

• The predicted "critical value" of selection for association was not observed in simulations.
• Loci remained associated to some extent across all simulated selection strengths.
• Simulations aligned with equilibrium analysis in other aspects, indicating a slow approach to equilibrium under weak selection.

Conclusions:

• The approach to equilibrium is significantly slower than predicted by equilibrium models, especially under weak selection.
• The slow approach to equilibrium allows for estimation of time since secondary contact.
• Findings have implications for understanding natural hybrid zones and evolutionary timescales.