Connecting effects of temperature below and above ground on bumble bee colonies (Bombus impatiens)

Declines in bumble bee abundance and diversity across continents have been linked to rising global temperatures associated with climate change and the urban heat island effect. Bumble bees are common, diverse, widespread, and are among the most highly contributing pollinators for a wide variety of wild plants and cultivated crops. Thus, the impact of rising temperatures will have a negative effect on not just the bees themselves, but also the wild and cultivated plants that depend on these animals. While a growing body of research has considered the effects of temperature on individual bees, much less is known about how rising temperatures may affect bees collectively at the colony level. Colony performance is heavily influenced by nest temperature, which affects brood development, colony growth, and reproductive output. To understand the effects of environmental temperature on the colony as a whole, we measured temperature inside simulated bumble bee nests both below and above ground. The results of our initial experiment suggest that bees in outdoor aboveground nests experience greater temperature extremes and daily temperature swings than bees in underground nests. Therefore, bumble bees in commercial box nests used for field crop pollination may experience greater stress than their counterparts nesting naturally underground. We plan to conduct further experiments this summer and next spring to study how nest temperature varies among a range of natural and commercial bumble bee nests, and we will assess how well bumble bee colonies are likely to cope with increased temperatures due to climate change and urbanization.