Size-dependent variation in thermal tolerance among tropical bee species

Abstract

Thermal tolerance is a key determinant of an organism's ability to survive and adapt to environmental changes, particularly in ectothermic insects, which rely on ambient temperature for physiological regulation. While recent research has advanced our understanding of thermal tolerance in insects, particularly in temperate environments, the roles of sociality and morphological traits in shaping this tolerance remain poorly understood in tropical bee species. In this sense, bees exhibit diverse social structures and morphological variations, offering a valuable opportunity to explore how these factors affect thermal tolerance. Here, we examined whether sociality and body size explain variations in thermal tolerance across 43 bee species (five social species and 38 solitary species) inhabiting a coastal environment in Mexico. Our findings revealed that smaller bees tend to have broader thermal tolerance ranges, characterized by the differences between critical thermal maximum (CT_max) and critical thermal minimum (CT_min). Although none of the thermal tolerance metrics differed between social and solitary species, our results highlight size-dependent thermal tolerance differences among bee species, suggesting that small-bodied species are more resilient to environmental fluctuations. Integrating these insights could help predict how variation in thermal tolerance among bees may affect their pollination services under future climate change scenarios.

Keywords: climate change; critical thermal maximum; critical thermal minimum; organism ectothermic; social bees; solitary bees.