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22 : The Promise of Polyandry


The Promise of Polyandry


Keith S Delaplane


(Professor of Entomology, University of Georgia, USA, and visiting sabbatical scientist, National Bee Unit)


I


have had the good fortune to live and work in the UK for much of the past year as a visiting sabbatical scientist at the National Bee Unit (NBU) in North Yorkshire, during which time I’ve given numerous lectures around the country about what I’m doing here – studying polyandry and its implications for beekeepers and honey bee health.


Polyandry is the term used to describe the practice of the honey bee queen mating with multiple males, usually around 15, and storing and using their sperm for the rest of her productive life. The result is a colony made up of many different subfamilies, or patrilines, the number of which equals the number of drones with which the queen mated. It appears to be an elaborate bid for the colony to achieve a high degree of


Keith Delaplane


genetic diversity which in turn can help it weather a range of environmental stresses.


Within-colony Genetic Diversity


High within-colony genetic diversity appears to be common in the higher social insects, although different groups pursue it in different ways. The ants and termites, for example, practise the functional opposite of polyandry – polygyny, or the use of multiple queens, each individually mated and all contributing brood and offspring to the common nest.


Optimising Colony Fitness


Multiple matings and high within-colony genetic variation are now seen to be relatively late evolutionary developments for optimising colony fitness. One can think of it as insurance through genetic diversification: one subfamily may be genetically advantaged toward food hoarding, another toward thermoregulation, or another toward resisting parasites. And in fact, parasites and pathogens are considered one of the most powerful selection forces for polyandry in social insects1,2,3


. A series of papers has shown a positive


relationship between the degree of queen polyandry (number of mates) and the resistance of that queen’s colony to chalkbrood and American foul brood4,5,6


. This string of


fundamental way honey bees handle diseases and parasites is not through genetic specialisation, but through genetic diversification. This is the kind of fundamental biology that should anchor sustainable bee health management, especially in this period in history when bee scientists and beekeepers repeatedly hold out genetics as a tool for managing honey bee health.


Are More Drones Better?


But if ‘more drones is better,’ then why did natural selection stop at 15 drones for the average queen? Why not 50 or 100? There must be moderating evolutionary constraints, two of which may be sexually transmitted diseases (such as deformed wing virus) and the risk to the queen from predation and other hazards associated with repeated mating flights. Whatever the constraints limiting drone numbers, we can


.


Similarly, there is a positive relationship between polyandry and colony population growth and weight gain7


papers comes to us from some of the best journals in science. They are also consistent with the larger idea that the


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Polyandry and its implications for beekeepers and honey bee health


August 2013 Vol 95 No 8


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