Polygenic adaptation: a unifying framework to understand positive selection

Most adaption processes have a polygenic genetic basis, but even with the recent explosive growth of genomic data we are still lacking a unified framework describing the dynamics of selected alleles. Building on recent theoretical and empirical work we introduce the concept of adaptive architecture, which extends the genetic architecture of an adaptive trait by factors influencing its adaptive potential and population genetic principles. Because adaptation can be typically achieved by many different combinations of adaptive alleles (redundancy), we describe how two characteristics - heterogeneity among loci and non-parallelism between replicated populations - are hallmarks for the characterization of polygenic adaptation in evolving populations. We discuss how this unified framework can be applied to natural and experimental populations. Increased capacities for sequencing and genotyping are enabling a more comprehensive understanding of the genetics of adaptation for diverse species. In this Perspective, Barghi, Hermisson and Schlotterer describe how polygenic adaptation can be studied using a framework of 'adaptive architecture' that unifies principles from the traditionally disparate fields of quantitative genetics and molecular population genetics.