Misaligned plastic and evolutionary responses of lifespan to novel carbohydrate diets

Diet elicits varied effects on longevity across a wide range of animal
species. For example, diets low in protein and high in
carbohydrate typically extend lifespan while diets high in protein tend to
reduce it. Although studies have also shown that diet-induced lifespan
changes can persist through transgenerational plasticity, whether such
changes lead to evolutionary shifts in lifespan remains unclear. In this
study we combine experimental evolution and phenotypic plasticity assays
to address this gap. Using Drosophila serrata, we investigated the
evolutionary potential of lifespan in response to four novel diets
spanning a carbohydrate-protein gradient. We also examined developmental
plasticity effects using a set of control populations that were raised on
the four novel environments. Our results show that although lifespan
evolved in response to changes in dietary carbohydrate concentration, the
plastic responses for lifespan differed from the evolved responses. The
direction of the evolved response (increased lifespan) observed on low
carbohydrate diets was in the opposite direction to the plastic response
(decreased lifespan). Our results imply that plastic responses to low
carbohydrates can be maladaptive for lifespan and misaligned with the
evolved responses, laying the groundwork for future investigations of
carbohydrate contributions to evolved and plastic effects on lifespan.