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CYCLICAL ENVIRONMENTAL CHANGES AS A FACTOR MAINTAINING GENETIC POLYMORPHISM. 2. DIPLOID SELECTION FOR AN ADDITIVE
Abraham B Korol1, Valery M Kirzhner1, Yeafim I Ronin1
1Institute of Evolution, University of Haifa, Mount Carmel, Haifa, 31905, Israel.
Summary
Polymorphism maintenance under stabilizing selection with a moving optimum is complex. Unequal gene action or dominance can stabilize polymorphism, leading to cycles or complex "supercycles" in population genetics.
Area of Science:
- Population Genetics
- Evolutionary Biology
- Theoretical Biology
Background:
- Polymorphism maintenance is crucial for evolutionary adaptation.
- Stabilizing selection with a moving optimum presents challenges to maintaining genetic diversity.
- Understanding the genetic architecture of traits is key to predicting evolutionary dynamics.
Purpose of the Study:
- To investigate polymorphism maintenance under stabilizing selection with a moving optimum.
- To analyze the conditions for global and local polymorphism stability in two-locus models.
- To explore the impact of gene action, dominance, and selection intensity on evolutionary dynamics.
Main Methods:
- Mathematical modeling of population genetics.
- Analysis of fitness functions, including logarithmically convex functions.
- Investigation of additive and non-additive gene action models.
- Examination of cyclical selection patterns and their effects on polymorphism.
Main Results:
- Global polymorphism requires specific fitness conditions for double homozygotes relative to heterozygotes, influenced by recombination and period length.
- Local polymorphism stability is possible even when homozygote fitnesses exceed heterozygote fitnesses.
- Cyclical optima do not maintain polymorphism with additive gene action at equal loci for logarithmically convex fitness functions.
- Non-equal gene action or dominance can create stable polymorphism with large attracting domains, especially with strong selection and close linkage.
- Cyclical selection can lead to forced cycles or complex 'supercycles' of polymorphism.
Conclusions:
- Polymorphism maintenance is sensitive to the genetic control of traits and environmental fluctuations.
- Non-additive genetic effects and cyclical selection introduce complex dynamics, potentially preserving diversity.
- The study highlights the importance of considering complex genetic architectures and dynamic environments in evolutionary theory.
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