Critical thermal maxima differ between groups of insect pollinators and their foraging times: Implications for their responses to climate change

Insects perform essential roles within ecosystems and can be vulnerable to climate change because of their small body size and limited capacity to regulate body temperature. Several groups of insects, such as bees and flies, are important pollinators of wild and cultivated plants. However, aspects of their thermal biology remain poorly studied, which limits predictions of their responses to climate change. We assessed the critical thermal maximum (CTMax) of bees and flies visiting flowers in urban and periurban areas in tropical and subtropical regions of the Americas. We also assessed the effect of the foraging time of the day on CTMax. Overall, we found that bees displayed higher CTMax than flies. Flies foraging in the morning and afternoon displayed similar CTMax while bees in the morning displayed a higher CTMax than in the afternoon. The results of this study suggest differences in the vulnerability to climate change between these two major groups of pollinators, with flies being more at risk.