Developmental nutrition modulates metabolic responses to projected climate change

The current policy has the world on track to experience around 3°C of warming by 2100. The responses of organisms to our warming world will be mediated by changes in physiological processes, including metabolic rate. Metabolic rate represents the energetic cost of living, and is fundamental to understanding the energy required to sustain populations. Current evidence indicates that animals have a limited capacity to adapt to warmer environments by reducing their metabolic rate. Consequently, animals may be more reliant on metabolic plasticity to ameliorate the thermodynamic effect of rising temperatures on physiological rates. However, metabolic plasticity is influenced by other environmental factors, including the nutritional quality of food. Elevated levels of atmospheric CO₂ are expected to reduce the protein and increase the carbohydrate concentration in plants, but we do not know how this will affect the response of metabolic rate to climate warming. Here we test the interactive effects of developmental dietary protein and carbohydrate concentrations on the metabolic plasticity of adult Drosophila melanogaster in response to a 3°C increase in temperature while accounting for variation associated with body mass and activity (resting metabolic rate). We show that the thermal sensitivity of resting metabolic rate is modulated by developmental nutrition with animals reared on nutritionally poor, low-protein diets showing the greatest increase in resting metabolic rate in response to simulated climate warming. We also show that if the nutritional quality of resources is unaffected by climate change, then temperature-induced increases in resting metabolic rate will be offset by decreases in mass, but the absolute energy requirements of animals will be elevated relative to current conditions despite this. If, on the other hand, temperatures rise and resources become more calorie-dense and carbohydrate-rich, then the resting metabolic rate of animals will remain relatively unchanged, but decreases in mass and activity may drive down the absolute energy requirements of animals. In the absence of evolutionary adaptation, these findings suggest that the combined plastic response of physiological, morphological and behavioural traits to temperature and nutrition may be an important determinant of the ultimate outcome of climate change for populations. A free Plain Language Summary can be found within the Supporting Information of this article.