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The B -value calculator: expected diversity under background selection
Jacob I Marsh1, Austin T Daigle1,2,3, Parul Johri1,2,4
1Department of Biology, University of North Carolina, Chapel Hill, NC 27599.
Biorxiv : the Preprint Server for Biology
|March 23, 2026
Summary
Background selection (BGS) shapes genomic diversity. We developed Bvalcalc, a Python tool, to analytically estimate B-values, crucial for understanding evolutionary processes and detecting selection across genomes.
Area of Science:
- Evolutionary Biology
- Population Genetics
- Genomics
Background:
- Background selection (BGS) is a significant evolutionary force impacting genomic diversity.
- Accurate estimation of B-values (diversity under BGS vs. neutrality) is vital for genomic inference.
Purpose of the Study:
- To develop an efficient analytical method for calculating B-values.
- To provide a user-friendly tool for estimating genomic diversity under BGS.
Main Methods:
- Extended and integrated existing theory to analytically estimate B-values without selective interference.
- Developed Bvalcalc, a Python command-line tool for genome-wide B-value calculation at single base-pair resolution.
- Incorporated modules for recombination maps, gene conversion, self-fertilization, population size changes, and unlinked effects.
Main Results:
- Bvalcalc enables efficient analytical calculation of expected B-values across the genome.
- The tool accounts for various evolutionary factors including recombination and population structure.
- Validated Bvalcalc against simulations and generated B-maps for human, fruit fly, and Arabidopsis.
Conclusions:
- Bvalcalc provides a robust method for estimating genomic diversity shaped by background selection.
- The tool facilitates null model development for demographic inference and selection detection.
- Bvalcalc is publicly available, supporting broader research in population genetics and evolutionary genomics.
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