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Honey Bees' Diversity Helps Keep Them Cool

Buzzing with activity, a honey bee nest is always busy. And thanks to the promiscuous behavior of the queen, which mates with multiple males, colonies are also genetically diverse. Now, scientists from the University of Sydney have made a connection in a June 2004 study. They suggest that genetic differences help workers conduct the task of temperature maintenance more efficiently.

In order for new broods to develop normally, honey bee nests need to stay between 90 and 97 degrees Fahrenheit. A warm 95 degrees Fahrenheit is optimal. Workers regulate the nest by huddling together when temperatures dip and fanning air out with their wings when the nest gets too hot.

The study shows that bees with different fathers respond differently to temperature changes, and as a result begin fanning at different times. This staggered behavior enables the nest to be heated and cooled gradually. In contrast, uniform colonies with workers from a single father tend to start and stop fanning at the same time, leading to more dramatic temperature swings. The scientists link differences in the bees' internal thermostats to their genetic diversity.

The study compared four genetically uniform colonies, in which artificial insemination was used to ensure that only one male fertilized the queen, with four colonies in which the queens mated freely with multiple males. After two sets of week-long temperature measurements, scientists found that nest temperatures fluctuated more in the single-father colonies.

After raising the ambient temperature to 104 degrees, they again observed that the internal nest temperature of the diverse colonies remained more stable than that of the uniform colonies. To test the idea that differences in internal thermostats were related to diversity, scientists used genetic markers to show that bees with different temperature thresholds for fanning were descended from different fathers.

Several explanations have been suggested for the queen bee's multiple mating behavior. But until now, few clear benefits of the resulting genetic diversity were known. This new research suggests that a genetically diverse colony can respond more appropriately to environmental changes without overreacting, thereby contributing to the fitness of the colony overall.

Sources: Science DOI: 10.1126/science.1096340, ScienceNOW Fischer 2004 (624):3

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