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Updated: Jan 20, 2026
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A Modified Lean and Release Technique to Emphasize Response Inhibition and Action Selection in Reactive Balance
Published on: March 19, 2020
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Additive genetic variance for fitness maintained by balancing selection.
Tim Connallon1, Peter Czuppon2,3
1School of Biological Sciences, Monash University, Clayton, Australia.
Evolution; International Journal of Organic Evolution
|January 19, 2026
Summary
Balancing selection can maintain high additive genetic variation for fitness, contrary to classical theory. Violations of equilibrium conditions like genetic drift and temporal fluctuations generate substantial fitness variation.
Area of Science:
- Evolutionary genetics
- Population genetics
- Quantitative genetics
Background:
- Additive genetic variation for fitness is surprisingly high in natural populations.
- This excess variation exceeds levels expected from deleterious mutations alone.
- Balancing selection is a potential mechanism for maintaining this variation.
Purpose of the Study:
- To investigate how violations of equilibrium conditions affect additive genetic variation for fitness under balancing selection.
- To re-evaluate the role of balancing selection in maintaining genetic variation for fitness.
Main Methods:
- Theoretical modeling of population genetics.
- Analysis of conditions deviating from equilibrium (genetic drift, temporal fluctuations).
Main Results:
- Genetic drift and temporal fluctuations in fitness parameters significantly increase additive genetic variation for fitness under balancing selection.
- Each locus under balancing selection can contribute substantially to overall fitness variation, comparable to thousands of loci at mutation-selection balance.
Conclusions:
- Classical population genetics theory underestimates the role of balancing selection in maintaining additive genetic variation for fitness.
- Deviations from equilibrium are crucial for understanding the high levels of fitness variation observed in natural and experimental populations.
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