Fig. 1.

Illustration of the non-genomic pathways through which paternal effects on offspring development can be achieved. Experiences of males (drugs, nutrition, toxin, age), particularly those experienced during early development, may lead to epigenetic alterations in the male germline (red circle) which are then transmitted to offspring with consequences for phenotypic variation. Alternatively, or likely in combination with these direct paternal effects, the experiences of a male prior to mating may lead to changes in mate quality or preference as assessed by the female at the time of mating. This assessment may then lead to differential prenatal and/or postnatal maternal investment in the growth and development of offspring generated from this mating with consequences for offspring phenotypic variation. Maternal investment may also vary as a function of paternally mediated variations in offspring phenotype during both the prenatal and/or postnatal periods. Differential maternal investment as a function of paternal experiences or offspring traits may serve either to enhance the transmission of paternal exposures or compensate for deficits in functioning that are induced by these environmental experiences.