A multilocus analysis of intraspecific competition and stabilizing selection on a quantitative trait

Area of Science:

• Population Genetics
• Quantitative Genetics
• Evolutionary Biology

Background:

• Quantitative traits are influenced by multiple genes and environmental factors.
• Intraspecific competition and density-dependent selection play crucial roles in population dynamics.
• Previous models often simplified the complex interplay of selection, competition, and genetic architecture.

Purpose of the Study:

• To derive the equilibrium structure of a multilocus model for quantitative traits under frequency- and density-dependent selection.
• To characterize the conditions leading to multilocus polymorphism and disruptive selection.
• To provide explicit formulas for genetic parameters at equilibrium.

Main Methods:

• Developed an additive, diallelic multilocus model.
• Assumed weak stabilizing selection relative to recombination to ignore linkage disequilibrium.
• Analyzed the equilibrium and stability structure based on model parameters.
• Investigated linkage effects for two loci analytically and for multiple loci numerically.

Main Results:

• Derived conditions for the maintenance of multilocus polymorphism and disruptive selection.
• Obtained explicit formulas for the number of polymorphic loci, allele frequencies, genetic variance, and disruptive selection strength.
• Showed that previously studied models are special cases of the derived model under weak overall selection.
• Demonstrated the impact of linkage on genetic diversity and selection patterns.

Conclusions:

• The model provides a comprehensive framework for understanding quantitative trait evolution under density-dependent selection.
• The strength of competition relative to stabilizing selection is critical for maintaining genetic variation.
• The findings have broad applicability to models of intraspecific competition and resource utilization.