Global effects of extreme temperatures on wild bumblebees.

Climate plays a key role in shaping population trends and determining the geographic distribution of species because of their limits in thermal and water tolerance. An evaluation of species tolerance to temperature changes can therefore help predict their potential spatial shifts and population trends triggered by the ongoing global warming. In this work, we focused on 39 bumblebee species, a major group of pollinators in temperate and cold ecosystems, across three continents, six biomes, and 20 regions (2,386 male specimens). We assessed both inter- and intraspecific variations in heat resistance in relation to body mass, local mean temperatures, and evolutionary relationships. Our results show a significant interspecific variability but a low inter-populational variability in heat stress resistance, supporting heat resistance as a species-specific trait. Moreover, cold-adapted species are much more sensitive to heat stress than temperate/Mediterranean species. Based on these results, we provide a mechanistic explanation for the specific variation in the recent population declines and range shifts in bumblebees following climate change. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.