Predicting barrier architecture and the genomic landscape of differentiation under polygenic divergent selection

This study investigates how patterns of genetic variation across a genome reflect the genetic architecture responsible for postzygotic reproductive isolation in a mainland-island model. Researchers derive a new expression for the effective migration rate, applicable to both neutral and divergently selected loci, while developing a numerical method to predict allele frequencies at these barrier loci.

Utilizing this approach, they determine neutral coalescence times along the genome and demonstrate how the findings from the mainland-island model can be adapted to estimate coalescence times in nonequilibrium demographic models.

The validity of their method is thoroughly tested using forward-in-time individual-based simulations, confirming that the -based approximation maintains accuracy across a wide range of parameters. The researchers focus on both scenarios involving a single barrier locus and a pair of barrier loci to determine the conditions under which their approximation performs optimally.

By applying their predictions, they explore how the genetic architecture of divergent selection influences barriers to gene flow, quantifying the effects of hitchhiking along the genome and assessing the impact of polygenicity on reproductive isolation.

The findings have significant implications for mapping barriers to gene flow using population genomic data, presenting approaches for both model-based inference and genome scan techniques based on summary statistics.