Warming and food restriction reveal trait-specific energy allocation in the desert lizard

Climate warming can affect ectotherms both directly, by raising body temperature and metabolic demand, and indirectly, by decreasing food availability through changes in prey dynamics. However, how these stressors jointly influence energy allocation in juveniles remains unclear. We conducted an experiment to examine how elevated rearing temperatures and food restriction impact body temperature, resting metabolic rate (RMR), and somatic growth in juvenile Phrynocephalus przewalskii. We examined body temperature, resting metabolic rate (RMR), and somatic growth under two thermal regimes and two food levels. Responses differed among traits. Warming increased body temperature, whereas food restriction had no clear effect on this trait. Food restriction reduced body mass, while effects on SVL growth were weaker. The clearest combined effect of warming and food restriction was found in RMR: food restriction reduced RMR only in juveniles reared under warm conditions. These findings reveal that simultaneous thermal and nutritional stress do not affect juvenile traits uniformly. Instead, their strongest combined effects were seen in metabolic maintenance rather than structural growth, indicating that physiological traits may serve as earlier indicators of climate-related energetic stress than body size alone.