Recombination accelerates adaptation across genetic architectures and demographic histories

Classic population genetics theory suggests that recombination influences the effectiveness of natural selection. However, it is unclear whether variation in recombination rate directly impacts adaptive capacity. To investigate this, researchers utilized forward-time simulations to study polygenic adaptation in populations transitioning to new environments.

They manipulated recombination rates by eightfold, utilized three different gamma distributions to model quantitative trait locus (QTL) effect sizes, and compared constant and contracted population sizes.

Across all conditions, higher recombination rates slightly expedited adaptation, reducing the time to achieve a new phenotypic optimum by 2-15%. This beneficial effect was more pronounced in constant-size populations as opposed to those that experienced a population contraction, but the impact was not influenced by genetic architectures.

To comprehend the underlying mechanism, researchers monitored linkage disequilibrium among adaptation-related QTL throughout the adaptation process. They discovered that beneficial alleles consistently exhibited a repulsion phase with one another and a coupling phase with deleterious alleles, both of which are indicative of Hill-Robertson interference.

Higher recombination attenuated both types of interference, implying that the benefit of recombination primarily stems from relieving interference among QTL. These findings suggest that interference among linked loci is the primary constraint on polygenic adaptation in this scenario, and demographic history plays a critical role in modulating the benefits of recombination.