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Effective size of a fluctuating age-structured population.
Steinar Engen1, Russell Lande, Bernt-Erik Saether
1Department of Mathematical Sciences, Norwegian University of Science and Technology, Trondheim. rlande@ucsd.edu
Genetics
|April 19, 2005
Summary
This study presents new formulas for the variance effective size in age-structured populations experiencing demographic and environmental changes. The findings reveal how population size fluctuations impact genetic diversity over time.
Area of Science:
- Population Genetics
- Theoretical Ecology
- Stochastic Demography
Background:
- Traditional effective population size theories assume constant environments and population structures.
- Real populations face dynamic changes due to demographic and environmental stochasticity.
Purpose of the Study:
- To derive formulas for variance effective size in age-structured populations with fluctuating size and age distribution.
- To analyze haploid and diploid populations under demographic and environmental stochasticity.
Main Methods:
- Utilized recent advances in stochastic demography.
- Developed a two-dimensional diffusion approximation for population size (N) and allele frequency (p).
- Calculated effective population size per generation and over longer time intervals.
Main Results:
- Derived effective population size formulas accounting for demographic and environmental stochasticity.
- Found that effective size per generation depends on N, generation time, and genetic/demographic stochasticity, but not environmental stochasticity.
- Incorporated deterministic growth and environmental stochasticity for long-term effective size calculations.
Conclusions:
- The derived formulas provide a more realistic estimation of effective population size in dynamic populations.
- Understanding these dynamics is crucial for predicting genetic diversity and evolutionary trajectories.
- This work advances the theoretical framework for studying effective population size in variable environments.