Heat and cold tolerance of feral and managed honey bees (Apis mellifera) in San Diego, California

Honey bees (Apis mellifera) are important crop pollinators globally, but extreme weather events and changing temperatures due to climate change may threaten the success of this species. Although we know that extreme temperatures can decrease survival of honey bees, less is known about how extreme temperatures affect feral honey bees given that they may be better adapted to extreme temperatures than managed honey bees. In Southern California, feral honey bees are genetically admixed with Apis mellifera scutellata, an African honey bee that may be better adapted to hot climates and potentially limited in its range by cold climates. In our research, we investigated the effect of extreme heat or cold on the survival of feral and managed honey bees. We measured the proportion of surviving bees after exposure to heat or cold shock, critical thermal maximum and minimum, and chill coma recovery time for feral and managed bees. Feral honey bees survived heat shock and cold shock better than managed honey bees, but there were no differences in CTmax, CTmin, or chill coma recovery time. We are currently replicating survival trials with a common garden design to confirm whether differences in survival were due to differences in environmental temperatures at our separate apiary sites (one for feral and one for managed bees). Our results suggest that feral honey bees in Southern California are better adapted to extreme temperatures than managed honey bees. Future honey bee research should consider this difference in thermal tolerances between feral and managed honey bee populations.