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Coalescent size versus coalescent time with strong selection.
1Department of Mathematics, University of Northern Iowa, Cedar Falls, IA 50614-0506, USA. campbell@math.uni.edu
Bulletin of Mathematical Biology
|June 5, 2007
Summary
Selection significantly reduces coalescent time more than cumulative population size. This impacts genetic diversity, decreasing heterozygosity more than segregating alleles, especially in smaller coalescents.
Area of Science:
- Population Genetics
- Evolutionary Biology
- Theoretical Biology
Background:
- The coalescent theory models the ancestral relationships within a population.
- Population genetics studies how genetic variation changes over time due to evolutionary forces.
- Selection's impact on the coalescent process is a key area of population genetics research.
Purpose of the Study:
- To analyze how natural selection alters the coalescent process in a population.
- To quantify the differential effects of selection on coalescent time and cumulative population size.
- To understand the implications for genetic diversity metrics like heterozygosity and segregating alleles.
Main Methods:
- Mathematical modeling of the coalescent process under selection.
- Comparison of coalescent and fixation times with neutral drift scenarios.
- Analysis of cumulative coalescent size and its relationship to population parameters (N and s).
Main Results:
- Selection reduces coalescent time more drastically than cumulative population size, particularly when the coalescent is small.
- Coalescent and fixation times are significantly shorter under selection (e.g., 70-95% reduction for Ns=10-100) compared to neutral drift.
- Reduction in cumulative coalescent size ranges from 17% to 65% for large populations (N=10^3-10^6) under selection.
Conclusions:
- Selection disproportionately shortens the time to common ancestry compared to the total number of ancestors.
- Heterozygosity, proportional to coalescent time, is reduced more by selection than the number of segregating alleles, which relates to cumulative size.
- These findings highlight selection's complex influence on population genetic diversity patterns.
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