Thermal tolerance varies with dim‐light foraging and elevation in large carpenter bees (Hymenoptera: Apidae: Xylocopini)

Abstract

1. Thermal tolerance has a strong predictive power for understanding the ecology and distribution of organisms, as well as their responses to changes in land use and global warming. However, relatively few studies have assessed thermal tolerances for bees.2. The present study aimed to determine whether the critical thermal maximum (CTmax) of carpenter bees (Apidae: genus Xylocopa Latreille) varies with different patterns of foraging activity and elevation. In addition, the influence of body size, body water content and relative age was examined with respect to their CTmax and differences in thoracic temperature (Tth) among species were evaluated.3. The CTmax of one crepuscular (Xylocopa olivieri) and two diurnal species (Xylocopa violacea and Xylocopa iris) of carpenter bees was assessed at sea level on the Greek island of Lesvos. To detect variation as a result of elevation, the CTmax of a population of X. violacea at 625 m.a.s l. was assessed and compared with that from sea level.4. Xylocopa olivieri displayed a similar CTmax to that of X. violacea but lower than that of X. iris. Body size, body water content, and relative age did not affect CTmax. In X. violacea, CTmax decreased with elevation and all three species have high Tth independent of ambient temperatures.5. The results of the present study are consistent with variations in CTmax predicted by broad spatial and temporal patterns reported for other insects, including honey and bumble bees. The implications of the results are discussed aiming to understand the differences in the foraging pattern of these bees.