Ecology: Key to bee-ing social

The social network of honeybee colonies is substantially influenced by microbes in their gut, according to a study published in Nature Ecology & Evolution. The presence of diverse bacteria in the gut increases the rate of social interactions among bees and is associated with increases in brain metabolites involved in sensory perception.

Microbes in the gut — the microbiome — are known to influence aspects of individual animal behaviours, such as aggression or nest mate recognition, and to affect hormone signalling to the brain. However, how these effects might influence social interactions within large groups is less well known.

Joanito Liberti and colleagues used automated video tracking to quantify the social interactions of laboratory-maintained honeybees (Apis mellifera carnica). The bees were maintained in colonies that had either an experimentally depleted microbiome or in ones that had been colonized by a diverse natural gut microbiome from donor bees. The authors reveal that bees with diverse microbiomes engaged in significantly more head-to-head interactions with other bees in the colony. However, these interactions were more random across the colony among bees with depleted microbiomes, who exhibited little social structure. Chemical and genetic analysis of brain and body tissues revealed that bees with natural, diverse gut microbiomes had higher abundances of metabolites and essential amino acids than microbiome-depleted bees. Several of these metabolites are known to have roles in brain function and energetics, with two in particular — serine and ornithine — being significant predictors of head-to-head interactions between bees.

The authors conclude that these findings emphasize the valuable role of the gut microbiome in determining the complex social lives of honeybees.