Mating with more than one drone (up to twenty in the case of the honey bee queen) results in a genetically diverse colony, and scientists are discovering the benefits that result from the diversity, at least in the short term. The benefits of genetic diversity in the long-term are difficult to establish because, essentially, only the queen reproduces.
Using instrumental insemination to create colonies that have been fathered by only one drone and comparing them to colonies where the queen was fertilized by mixed semen from several drones, Julia Jones and her colleagues at the University of Sydney found that the diverse groups were able to keep the temperature in their nests more stable than the genetically uniform colonies because bees from different lineages started fanning at slightly different temperatures, while bees in the homogenous colony all started fanning at the same time.
Other evidence of the adaptive value of genetic diversity was explored by Cornell University scientist Thomas Seeley in a study with Heather Mattila and in another with David Tarpy. Both studies compared genetically diverse colonies, where the queen had been instrumentally inseminated by sperm from ten or fifteen drones, to genetically uniform colonies, where the queen had been inseminated by sperm from only one drone.
The genetically diverse colonies proved to be more resistant to bacteria, built honeycomb at a 30 percent faster rate than homogenous colonies, collected 39 percent more nectar and pollen, and after two months had five times the population of the single father colony. Swarms from diverse colonies also founded new colonies faster than swarms from genetically uniform colonies, another valuable attribute.
Paul Schmid-Hempel and Boris Baer in Zürich compared queen bumblebees that were instrumentally inseminated with sperm from the same drone with others who were inseminated with a mixture of sperm from four drones. The queens then founded colonies in a meadow near Basel, and their progress was tracked. The multi-father colonies were healthier, suffered from much less parasitism than the single-father colonies, and were twice as prolific, further confirmation of the benefits of genetic diversity.
A honey bee queen can lay fifteen hundred to three thousand eggs on a good day, and she can lay as many as half a million eggs in her two- or three-year lifetime. Her eggs are only reared to adulthood if there are enough workers to feed and incubate them.
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