Maternal and paternal sugar consumption interact to modify offspring life history and physiology

Intergenerational effects on offspring phenotypes occur in response to variation in both maternal and paternal nutrition. Because the combined maternal and paternal effects are rarely considered together however, their relative contributions, and the capacity for interactions between parental diets to shape offspring life history and physiology are not understood. To address this, we altered sucrose levels of adult fruit flies (Drosophila melanogaster) prior to mating, across two generations, producing parent-parent and parent-offspring combinations that were either matched or mismatched in dietary sucrose. We then measured lifespan, fecundity, body mass, and triglyceride levels in parents and offspring. We reveal complex non-additive interactions, that involve diets of each parent and offspring to shape offspring phenotypes, but the effects were generally not consistent with an adaptive response to parental diet. Notably, we find that interacting parental flies (sires and dams) lived longer when their sucrose treatments were matched, but they produced shorter-lived offspring.