Meeting Abstract
Thermal extremes and abrupt shifts in temperature will impose physiological stress on organisms, and may increase susceptibility to other extrinsic factors, such as disease. It has been implied that ongoing changes in the thermal environment are negatively influencing bumble bees and their functioning as key pollinators, but we have limited information of causal effects of temperature on relevant measures of bumble bee health. To fill this void, we have used the model host-parasite system of bumble bees and their trypanosome parasite Crithidia bombi, together with life history and immune measures. We have specifically investigated the thermal mismatch hypothesis, which predicts reduced performance following an abrupt shift away from an acclimation temperature, and the thermal stress hypothesis, which suggests costs experienced under extremes will compromise an organism’s ability to function, including the fighting of infections. Results suggest that infection outcomes may be robust to thermal variability within the range of normal daily temperatures, but that exposure to realistic heatwaves can be detrimental to bumble bee immunity and other fitness-related traits. Underlying these effects may be antagonistic relationships between the heat stress and immune responses. Overall, the results suggest that thermal variability will have important consequences for bumble bee physiology and biotic interactions, and with ongoing climate change these effects could compound with other bumble bee life cycle effects to the detrimental of fitness and population health.
