Genetic differences among honey bees (Apis mellifera) performing the task of thermoregulation

Thermoregulation of the colony is one of the most important tasks performed by honey bee (Apis mellifera) workers. The temperature of the brood nest must be stringently controlled to ensure full pupal development. When the temperature of the nest increases middle-aged workers congregate at the nest entrance and fan their wings in order to drive out warm air, this behaviour is known as fanning.

Honey bee queens typically mate with multiple males to produce genetically diverse colonies comprised of multiple subfamilies. It can be hypothesised that if these subfamilies vary in their sensitivity to stimuli for performing specific tasks, such as fanning, this might result in some subfamilies carrying out those tasks more often than other subfamilies. Therefore it can be hypothesised that more genetically diverse colonies are more likely to accurately regulate the temperature in the hive than colonies with fewer subfamilies because they would have a larger distribution of temperature thresholds at which they would act to regulate brood nest temperature. 

The ambient temperature of the room housing the hive was manipulated to between 25 and 40ºC for two experimental colonies, and collections were made of individual bees performing fanning behaviour. I increased the ambient temperature from 25 to 40ºC in one-degree increments and sampled bees fanning at each temperature. I also sampled fanning bees while decreasing the ambient temperature from 40 to 28ºC.

The intracolonial diversity for each colony was measured using microsatellite markers. Analysis revealed a significant difference in the representation of subfamilies fanning at different temperatures. In addition there was a significant difference between overall subfamily proportions in the colony and the proportion of subfamilies fanning at different temperatures. These results suggest that different subfamilies begin the task of fanning at different temperature stimuli. Thus subfamilies with low temperature thresholds may perform the task more often than subfamilies with higher thresholds. In general these results suggest that bee colonies may benefit from intracolonial genetic variance generated via polyandry, as this variance modulates activity, reducing the possibility of large skews in the number of individuals engaged in any particular task.