Pleiotropic models of polygenic variation, stabilizing selection, and epistasis

Area of Science:

• Evolutionary genetics
• Population genetics
• Quantitative genetics

Background:

• Polymorphic populations often exhibit polygenic traits linked to fitness.
• Apparent stabilizing selection can be observed on these traits, irrespective of direct selection pressures.

Purpose of the Study:

• To investigate the mechanisms causing apparent stabilizing selection on polygenic traits in polymorphic populations.
• To compare different genetic variability models in maintaining this apparent selection.

Main Methods:

• Analysis of genetic system equilibria under selection, mutation, and migration.
• Comparison of mutation-migration-selection balance, overdominance, and epistasis models.
• Quantification of apparent stabilizing selection strength relative to genetic variance and locus number.

Main Results:

• Apparent stabilizing selection is expected when genetic systems reach equilibrium, particularly under mutation-migration balance.
• The strength of apparent stabilizing selection in mutation-migration balance models is proportional to Vm/Vg.
• Epistasis models can result in apparent stabilizing selection as strong as total selection on the phenotype.

Conclusions:

• Apparent stabilizing selection on polygenic traits is a common outcome of genetic system dynamics in polymorphic populations.
• The specific genetic architecture, including epistasis, influences the strength of apparent stabilizing selection and genetic load.