Indirect genetic effects

The concept of Indirect Genetic Effects (IGEs) captures the insight that trait expression often receives inputs not only from the genotype of the bearer of the trait (the focal individual), but also from the phenotype of other individuals with whom the focal individual interacts. This concept is intuitive if we consider behavior: how an animal acts is often influenced to some degree by how other individuals around it behave. Consequently, an animal’s behavior is not only shaped by inputs from its own genotype, but also from the genotypes of those other individuals. The variety of traits that exhibit this architecture is surprisingly large, including not only many behaviors but also morphological and life history traits, and the relevant inputs can arise not only from behavioral interactions but also from ecological relationships. Taking into account this broader view of trait architecture brings insight into how phenotypic and genetic evolution proceed.