Maternal-Offspring Interactions: Reciprocally Coevolving Social Environments.

Maternal-zygotic co-evolution is one of the most common examples of indirect genetic effects. I investigate how maternal-zygotic gene interactions affect rates of evolution and adaptation. Using comparably parameterized population genetic models, I compare evolution to an abiotic environment with genotype-by-environment interaction (G × E) to evolution to a maternal environment with offspring genotype-by-maternal environment interaction (G × Gmaternal). There are strong parallels between the 2 models in the components of fitness variance but they differ in their rates of evolution measured in terms of ∆p, gene frequency change, or of ∆W, change in mean fitness. The Price Equation is used to partition ∆W into 2 components, one owing to the genetic variance in fitness by natural selection and a second owing to change in environment. Adaptive evolution is faster in the 2-locus model with G × Gmaternal with free recombination, than it is in the 1-locus model with G × E, because in the former the maternal genetic environment coevolves with the zygotic phenotype adapting to it. I discuss the relevance of these findings for the evolution of genes with indirect genetic effects.