The interaction of biological network topology and mutation effects in complex trait evolution

The genetic architecture of complex traits can be described through three complementary frameworks: the additive genetic variance-covariance matrix $G$ (quantitative genetics), summarizing the genetic architecture of a set of traits; the distributions of phenotypic and fitness effects of new mutations (population genetics), which together with allele frequency dynamics determine which variants segregate; and the regulatory network topology that conditions both (systems biology). This review synthesizes how the evolutionary genetics of complex traits and the systems biology perspective are related: network topology constrains the distributions of phenotypic and fitness effects of new mutations, influencing the genotype-phenotype map. Then, over evolutionary time, stabilizing selection can reshape topology for increased robustness. Empirical support for these processes is reviewed: genome-scale perturbation experiments, network simulations, and evidence that stabilizing selection progressively sculpts regulatory networks toward additivity. Perspectives and future research directions are discussed.