Is heterozygous advantage necessary for polymorphism in one-locus two-allele systems?

Area of Science:

• Population genetics
• Evolutionary biology
• Mathematical modeling

Background:

• Density-dependent selection influences population dynamics and genetic variation.
• Traditional models often assume heterozygote superiority for maintaining genetic polymorphism.
• Understanding selection pressures is crucial for predicting evolutionary trajectories.

Purpose of the Study:

• To model density-dependent selection in a continuously reproducing diploid population.
• To investigate conditions for protected polymorphism in a two-allele, one-locus system.
• To explore the role of simultaneous fertility and viability selection.

Main Methods:

• Development of a mathematical model using differential equations.
• Definition of genotypic fitness based on contribution to population growth rate.
• Analysis of conditions for protected genetic polymorphism.

Main Results:

• A model of density-dependent selection was developed for a diploid population.
• Conditions for protected polymorphism were mathematically derived.
• Genetic polymorphism can be maintained without heterozygote superiority when both fertility and viability selection are present.

Conclusions:

• Simultaneous operation of fertility and viability selection can maintain genetic polymorphism.
• Heterozygote superiority is not a mandatory condition for polymorphism in diallelic one-locus systems under these conditions.
• The study provides new insights into the maintenance of genetic diversity in populations.