Archaic introgression and the distribution of shared variation under stabilizing selection.

Area of Science:

• Evolutionary genetics
• Population genetics
• Genomics

Background:

• Stabilizing selection maintains optimal phenotypic values in populations.
• Natural populations are dynamic and often structured, experiencing admixture and introgression.
• Previous studies focused on trait dynamics in single, steady-state populations.

Purpose of the Study:

• To model the genetic architecture of traits under stabilizing selection in admixed populations.
• To investigate the dynamics of introgressed ancestry around trait-affecting loci.
• To explain overlapping patterns of depleted introgressed ancestry in humans and Neanderthals.

Main Methods:

• Utilized the site-frequency spectrum to model trait genetic architecture.
• Employed a deterministic two-locus model to predict introgressed ancestry reduction.
• Conducted individual-based simulations to validate model predictions.

Main Results:

• Introgressed ancestry is significantly depleted around loci influencing traits under stabilizing selection.
• Bidirectional introgression, like between humans and Neanderthals, results in shared regions of depleted introgressed ancestry.
• Depleted introgressed ancestry regions in Neanderthals overlap with Neanderthal-ancestry deserts in humans.

Conclusions:

• Stabilizing selection can create detectable patterns of reduced introgressed ancestry around trait loci.
• Shared phenotypic optima between diverged populations may explain overlapping patterns of introgressed ancestry depletion.
• The findings provide a framework for studying trait evolution in complex, admixed populations.