Biotic and abiotic factors influencing bees’ physiological thermal limits

Critical thermal limits are the minimum (CT_Min) and maximum (CT_Max) temperatures at which an animal can maintain muscle control. These physiological traits are key for our understanding of an organism’s ecology and evolution, as well as to predict the responses to changes in land use and climate. Bees are essential pollinators of wild and cultivated plants and interest in assessing their critical thermal limits is rapidly increasing. Based on on-going studies and a literature review, we discuss the biotic (body size, sex, nutrition) and abiotic (pesticides, spatial gradients) factors that influence bees’ critical thermal limits. Only nine studies are available, most of them are from North America and are focused on understanding changes in CT_Max in the context of landscape alteration, although some studies addressed its relationship with bees’ invasiveness potential and foraging patterns. Bees appear to display a stronger response in CT_Min than in CT_Max, except to acute exposures to sublethal doses of pesticides, which increases CT_Max. Despite the small number of studies, these differ in methodology, which likely affects estimates of bees’ critical thermal limits and thus potentially limit comparisons across taxa and regions.