Understanding how bees respond to global change is essential to conserving the ecosystem services they provide, but few have utilized physiological limits to predict responses. Thermal limits have been shown to have strong predictive power in explaining population changes. Water content limits may also be strong predictors, but the importance of water content in understanding global change has not been well explored. Here, we examine how urbanization alters critical thermal maximum (CTmax) and critical water content (CWC) for three bee genera: striped sweat bees (Agapostemon), honeybees (Apis), and bumblebees (Bombus). We sampled bees from three urban and three rural sites in Toledo, Ohio. We calculated CTmax and CWC for each bee taxa at all sites. We also took field measurements of body temperature and water content, and calculated safety margins for each genus.
Results/Conclusions
We found significant differences in thermal and water content limits between taxa. Moreover, bumblebees and striped sweat bees were closer to their thermal limits in more urban locations, while honeybees were closer to their water content limits. This points out the need to better investigate desiccation, along with temperature, as potential mechanisms underlying the biological effects of global change. These results suggest that bees have differential sensitivities to environmental change and managing for diverse bee communities and associated pollination services in the face of global change may require mitigating both changes in temperature and water.