Honey Bee Behavior...oh wait, I mean "Behaviour".

An interesting study that I found recently was all about Honey Bees (Apis spp). "Genetic Diversity in Honey Bee Colonies Enhances Productivity and Fitness", written by Heather R. Mattila and Thomas D. Seeley in 2007, looks at how genetic diversity within a hive can alter the overall togetherness of a colony.

Initially, it was thought that, within socialising species of insects, like the bees, wasps, and ants (basically, anything that is of the Order Hymenoptera), colonies will be more unified and work more efficiently if the individuals are all related to each other, a.k.a. a lack of genetic diversity. However, there is an interesting phenomenon noted by scientists as of late: polyandry is a reoccuring phenomenon among socialising insects. Polyandry, where one reproductive female (the queen) mates with two or more reproductive males (called drones), causes a lack of relatedness of the other females (called workers; they're infertile) within the colony.

Now, we've all heard of swarming, right? Swarming is when the queen and several thousand of her workers relocate to a new nesting site. This, however, is extremely risky: the study mentions how, once relocated, only 20% of colonies actually survives in its first year! This is due to workers not gathering enough resources for the colony, and they starve to death come winter-time. These known facts gave the researchers something to work with. They wanted to see how colonies which are genetically diverse (polyandry colonies) compare to uniformly genetic colonies when a swarming event occurs.

21 colonies were used for this experiment, with 12 of them having a queen that was inseminated with sperm from a unique set of 15 drones. The remainding 9 colonies were inseminated with sperm from a single drone. The honey bees were then relocated to a new nest site, simulating what would happen if a swarming event occured, and measurements of comb construction, brood rearing, foraging activity, food storage, population size, and overall weight gain were the comparisons between the two groups.

RESULTS TIME!!!

Interestingly enough, colonies which were more genetically diverse were much better off than colonies that were more related to each other. The polyandric bees were able to construct about 30% more comb than the other group within a two week period (after the "swarming" event). In addition, foraging levels were also significantly greater with the genetically diverse colonies: in the two weeks after the relocation, the diverse colonies had gathered about 39% more stored food than the uniform colonies. When honey was starting to be produced between the two groups of colonies, guess which group was about twice as heavy as the other? Yup, the polyandric bee colonies!

What about new workers that are being produced? Well, the genetically diverse colonies got that one covered too! The production of new workers in genetically uniform colonies were clearly outmatched by genetically diverse colonies within the first month after the swarming event. The brood rearing was increasing continually (until the end of August, which is Autum in the Northern Hemisphere), whereas the genetically uniform colonies were producing low numbers of workers over the same period of time. Due to this, there were many more workers in the genetically diverse versus the genetically uniform colonies: with an average of 26,700 (± 1830) individuals in comparison to 5,300 (± 2,400) individuals, there really is no comparison!

It's pretty interesting that genetically diverse colonies can work better together and produce more fit colonies than genetically uniform ones. We've all heard that each worker is a "sister" to the other workers in a hive, and while in many cases it's correct, we should start calling them "half-sisters"! I guess having multiple gene lines in one colony would be beneficial in multiple ways; a disease ploughing through honey bees can be slowed down or even stopped if there are variations between each individual.  I'm now curious as to the proportion of bee colonies (and ant and wasp colonies) are polyandric in the wild in comparison to genetically uniform colonies. Perhaps this can help the issue of declining Apis spp.  around the world? More research would have to be done before that statement is valid!

Thanks!

~Mel

PS: Forgive me if I wrote in American, my Kiwi friends! I tried!

Picture from: http://www.nmhoney.com/nmhoney/Sub%20Files/Pictures/Bee%20Swarm%20in%20Apple%20tree-orchard.jpg

You can find the study at:
http://www.sciencemag.org/content/317/5836/362.full