During swarming, is blood thicker than honey?
Answer: No, workers do not prefer to stay with their sister queens.
The well-known phrase "blood is thicker than water" has always puzzled me. I fully understand that blood, in this context, is a metaphor for relatedness, specifically genetic relatedness by common descent (i.e., blood relatives for those who share a recent genetic ancestor). But water? Really?! Why water? I suppose is because there is no obvious opposite of blood, and water simply seems like an logical or convenient alternative. But if the analogy is suppose to show the importance of one's relatedness, shouldn't the alternative be something that is actually thicker than blood? In other words, wouldn't it make more sense, for example, for the phrase to go "blood is thicker than honey"?
I evoke this phrase because relatedness is critical to the functioning of honey bee colonies. This is because, put very simply, a colony is nothing more than one large kin group or family. The mother queen begets all of the offspring in the colony, so that all of the workers are her daughters and all the drones are her sons. This does not imply, however, that everyone is equally related. In fact, because queens mate with an average of 12 drones, the workers can be differentially related to each other. Workers that share the same father, known as supersisters, are highly related to each other, and in fact share 75% iof the their genes in common. Workers that have different fathers, known as half sisters, have only 25% of their genes in common. As a result, there is much theory that has concentrated on how individuals within such complex kin groups ought to behave towards one another. It would make sense, for example, that worker bees prefer to interact with their supersisters compared to their half sisters.
This potential conflict of genetic relatedness could have profound repercussions during certain phases of a colony's life history, perhaps most importantly during swarming. Swarming, of course, is when the mother queen departs the nest with the majority of the adult worker force to establish a new colony, leaving behind multiple daughter queens, one of which will reclaim the throne of the original nest. Because workers are related to their mother by 50%, to their supersisters by 75%, and to their half sisters by only 25%, one could predict that—if blood is indeed thicker than honey in bees—if the replacement queen is a suspersister of a worker, then that worker would prefer to stay rather than go with the swarm. If the replacement queen is a half sister, however, the worker might prefer to leave with the mother queen in the swarm.
It is this choice that a recent study tested by sampling bees in swarming colonies. A group of Cornell researchers, led by Juliana Rangel, allowed three hives to swarm naturally. They then extracted the DNA from sample of workers in each swarm, workers that remained back in their original colonies, and the queens that would have inherited the natal nests. They used molecular genetics to determine the paternity of each sample; that is, who was related to who. Their findings clearly show that there is no strong preference for workers to either depart with the mother queen or remain in the original colony based on the relatedness of the replacement queen.
These results demonstrate that while blood may be thicker than water, it does not appear to be thicker than honey.
Rangel, J., H. R. Mattila, and T. D. Seeley. (2009). No intracolonial nepotism during colony fissioning in honey bees. Proceedings of the Royal Society, B, 276: 3895-3900.