Fig 1. Overall framework of selection bridging population genetics and quantitative genetics models.

In this conceptual framework, selection on genotype is mediated by fitness-relevant phenotype and manifests in allele frequency changes and genetic variation patterns. In any specific environment, genotype and environment together shape the phenotype of an individual, which in turn determines the fitness. In addition to its direct effect on the phenotype (solid purple arrow), the environment also modifies the genotype-to-phenotype mapping (i.e., genotype-by-environment interaction; indicated by the dotted purple arrow) and phenotype-to-fitness mapping (dashed purple arrow). Through interactions with other evolutionary forces (indicated by the brown plus sign), natural selection shapes the allele frequency trajectory over time and leaves footprints in genomic variation in present-day populations.