MAINTENANCE OF POLYGENIC VARIATION IN SPATIALLY STRUCTURED POPULATIONS: ROLES FOR LOCAL MATING AND GENETIC REDUNDANCY

Area of Science:

• Evolutionary biology
• Population genetics

Background:

• Heritable genetic variation is essential for evolution, but its maintenance mechanisms are not fully understood.
• Mutation-selection balance is a key factor, but its ability to explain high heritability (0.5) in natural populations is debated.
• Existing models often assume panmictic (randomly mating) populations, potentially overlooking spatial effects.

Purpose of the Study:

• To investigate how isolation by distance affects genetic variation maintenance under mutation and optimizing selection.
• To determine the role of genetic redundancy in this process.
• To explore the impact on neutral alleles and heterozygosity.

Main Methods:

• Monte Carlo simulations were employed to model populations with isolation by distance.
• The simulations examined polygenic traits under optimizing selection.
• Various dispersal patterns and selection strengths were analyzed.

Main Results:

• Isolation by distance substantially increases total genetic variation in continuous populations, particularly with genetic redundancy.
• Isolation by distance alone has a minor effect on neutral allele variation.
• The combination of isolation by distance and genetic redundancy maintains high variation under strong stabilizing selection.
• Variation maintenance is largely independent of selection strength and dispersal variance within a moderate range.
• Individual heterozygosity increases in locally mating populations under strong selection.

Conclusions:

• Isolation by distance is a significant factor in maintaining heritable genetic variation, especially when coupled with genetic redundancy.
• This spatial structure allows independent mutation and drift in subpopulations, preserving diverse genotypes.
• The findings challenge the sufficiency of panmictic models for explaining high genetic variation in natural populations.
• The study provides insights into the spatial distribution of genetic and phenotypic variation influenced by selection and dispersal.