Variation in worker C:N:P stoichiometry and energy storage across a climate gradient in the Aphaenogaster rudis species complex

An increasing number of studies have demonstrated intraspecific variation in elemental composition of organisms, particularly in plants. However, relatively few studies have assessed patterns and possible mechanisms of intraspecific variation in carbon (C), nitrogen (N), and phosphorus (P) in animal consumers across a large geographical scale, and to our knowledge, none have been done on social insects. In this study, we investigated this variation in a temperate North American ant species complex, Aphaenogaster ruidis. This species complex occurs across a large latitudinal gradient and thus, experiences a wide range of climatic conditions and this may lead to variation in body elemental composition. Our results showed that ant pupal C, N, and P body content was unaffected by mean annual temperature (MAT) and mean annual precipitation (MAP). In contrast, an increase in either of the more variable climate predictors, diurnal range temperature (DRT) and annual precipitation seasonality (APS), resulted in an increase in C and decrease in N and P content in ant pupae. These results suggest that increasing climate variability may shift ant pupal stoichiometry towards C storage. Understanding the physiological mechanisms underlying these patterns should provide important insight into deciphering whether and how climate change may affect the availability of these important macronutrients in animal consumers.