Phenotypic Plasticity, Pleiotropy, and the Growth-First Theory of Imprinting

Abstract

The kinship theory of genomic imprinting suggests that parent-of-origin-dependent gene expression is the consequence of asymmetric selection on maternally and paternally inherited alleles. The theory has been most thoroughly developed in the context of early growth and development but applies, in principle, to any trait. The taxonomic and functional distribution of imprinted genes suggests that intragenomic conflict over maternal resources may play a particularly important role in the evolution of genomic imprinting in mammals, with those traits being the primary drivers of the acquisition of imprinted gene expression. In this scenario, imprinted gene effects on other traits (e.g., certain aspects of cognition and behavior) emerge initially as an epiphenomenon. However, once the gene is imprinted, more subtle selection asymmetries can have substantial consequences for the evolution of these traits. In this chapter, I motivate and formalize this “growth-first” theory of imprinting and lay out predictions that could be tested by future experiments.