The Effects on Neutral Variability of Recurrent Selective Sweeps and Background Selection

Area of Science:

• Population genetics
• Evolutionary biology
• Genomics

Background:

• Hitchhiking, caused by selective sweeps or background selection, influences genetic variability and adaptive evolution.
• Previous models often assumed selective sweeps are instantaneous, potentially limiting accuracy.

Purpose of the Study:

• To investigate the impact of relaxing the assumption of negligible sweep duration in models of hitchhiking.
• To derive new expressions for neutral variability and selective sweep effects under recurrent selection.
• To test theoretical predictions against simulations in Drosophila melanogaster.

Main Methods:

• Developed new theoretical expressions for neutral variability and recurrent selective sweeps.
• Performed multilocus simulations with realistic parameters for Drosophila melanogaster.
• Compared theoretical predictions with simulation results, considering recombination and mutation.

Main Results:

• Theoretical predictions showed approximate agreement with simulation results in the presence of crossing over.
• Background selection appears to be the primary driver of observed relationships between recombination rate and synonymous site diversity/adaptive evolution in Drosophila.
• Selective sweeps and population size changes are necessary to explain distortions in the site frequency spectrum.

Conclusions:

• The duration of selective sweeps is a relevant factor in population genetic models.
• Background selection plays a significant role in shaping genetic diversity and evolution.
• Combined effects of background selection, selective sweeps, and population size changes are crucial for a comprehensive understanding of Drosophila population genomics.