Studying models of balancing selection using phase-type theory.

Area of Science:

• Evolutionary genetics
• Population genetics

Background:

• Balancing selection (BLS) is crucial for maintaining genetic variability in essential genes.
• Understanding BLS's evolutionary significance requires analyzing its impact on polymorphism patterns.

Purpose of the Study:

• To analyze models of balancing selection (BLS) acting on a biallelic locus.
• To investigate the effects of long-term BLS, recent population size changes, and recent BLS on linked neutral regions.

Main Methods:

• Utilized phase-type theory, a mathematical tool for continuous time Markov chains.
• Examined polymorphism patterns including nucleotide diversity, segregating sites, site frequency spectrum, and linkage disequilibrium (LD).

Main Results:

• Long-term BLS affects small genomic neighborhoods, detectable when equilibrium frequencies are near 50% or after population size reduction.
• Recent BLS on a new mutation reduces linked diversity, skews variant frequencies, and elevates LD, mimicking but weaker than selective sweeps.
• Non-equilibrium patterns under recent BLS persist longer than under selective sweeps, enhancing detectability.

Conclusions:

• Balancing selection significantly shapes genetic diversity patterns in linked regions.
• Recent BLS leaves a longer-lasting signature than selective sweeps, offering a potential window for detection.
• The study provides a framework and tools for analyzing BLS models in population genetics research.