Variation in plasticity in response to combined thermal-nutritional stress is genetically independent between sexes and across traits

Abstract

AbstractPhenotypic plasticity helps animals to buffer the effects of increasing thermal and nutritional stress created by climate change. Studies have shown that plastic responses to single and combined stressors can vary among genetically diverged populations. However, less is known about how plasticity in response to combined stress varies among individuals within a population or whether such variation changes across life-history traits. This is important because individual variation within populations shapes population level responses to environmental change. Here, we used isogenic lines ofDrosophila melanogasterto assess plasticity of egg-adult viability and sex-specific body size for combinations of two temperatures (25°C or 28°C) and three diets (standard diet, low caloric diet, or low protein:carbohydrate ratio diet). Our results reveal substantial within-population genetic variation in plasticity for egg-to-adult viability and wing size in response to combined thermal-nutritional stress. This genetic variation in plasticity was a result of cross-environment genetic correlations that were generally < 1 rather than changes in the expression of genetic variation across environments. Cross-sex genetic correlations for body size were weaker when the sexes were reared in different conditions, suggesting wing size has the potential to evolve independently across sexes. Further, our results suggest that plasticity in egg-adult viability is genetically independent from plasticity in body size. By quantifying plasticity in response to combined stress between sexes and across traits, our study aims to develop a more nuanced understanding of the potential for populations to adapt to ongoing climate change.