Deviations from Hardy-Weinberg proportions for multiple alleles under viability selection

Area of Science:

• Population Genetics
• Evolutionary Biology
• Molecular Evolution

Background:

• Hardy-Weinberg proportions (HWP) deviations due to viability selection have been previously limited to two-allele systems.
• Understanding genetic variation requires analyzing deviations from HWP in multiallelic systems.

Purpose of the Study:

• To extend the analysis of deviations from Hardy-Weinberg proportions to autosomal loci with multiple alleles under constant viability selection.
• To derive fixation indices (FIS statistics) for homozygotes (fii) and heterozygotes (fij) in a multiallele viability model.
• To characterize the pattern of HWP deviations at stable equilibrium for multiallelic polymorphisms.

Main Methods:

• Mathematical derivation of fixation indices (fii and fij) for homozygotes and heterozygotes under a multiallele viability selection model.
• Derivation of expressions for fii and fij specifically for multiallelic polymorphisms at stable equilibrium.
• Application of the derived model to analyze published data for the beta-globin locus in West African human populations.

Main Results:

• Expressions for homozygote (fii) and heterozygote (fij) fixation indices were obtained for the multiallele viability model.
• At stable equilibrium, multiallelic polymorphisms exhibit a global heterozygote excess and a deficiency of each homozygote.
• Analysis of beta-globin locus data illustrates the application of these findings.

Conclusions:

• The derived pattern of HWP deviations (heterozygote excess, homozygote deficiency) can serve as an indicator of stable multiallelic polymorphism driven by viability selection.
• This framework provides a method for detecting viability selection in multiallelic systems.
• The study highlights the importance of considering multiple alleles when assessing population genetic structure and evolutionary forces.