UC San Diego

Honey bees (Apis mellifera) provide pollination services for many crops globally, but extreme weather and changing temperatures due to climate change may threaten the health of this species. Although we know that honey bee survival can decrease due to thermal stress, we know less about how thermal stress affects feral honey bees given that they are potentially adapted to higher temperatures in certain climates. Our research investigated the effect of extreme heat and cold on feral and managed honey bees in San Diego County, California. In this region, managed honey bees are pure European Apis mellifera, while the majority of feral honey bees are genetically admixed with Apis mellifera scutellata, from Africa, which are thought to be limited in their range by cold and to be more tolerant of heat. We measured individual survival between feral and managed honey bees after exposure to incubator heat shock or cold shock, critical thermal maxima and minima, and chill coma recovery time. Feral bees had higher survival compared to managed bees following heat shock or cold shock, but they did not differ with respect to CTmax, CTmin, or chill coma recovery time, suggesting that the effects of temperature upon survival require some time to manifest. Thus, the range of scutellata hybrids may not be constrained by individual survival following cold exposure but by colony-level effects or broader environmental effects linked with colder climates. These hybrids are, however, evidently better adapted to warmer conditions compared to pure European honey bees.