4.3.2. Determination of honey bee colony density using genetic markers
The difficulty of locating cryptic honey bee nests for density estimation can be overcome by exploiting their mating behaviour. Drones fly to drone congregation areas (DCAs) to find sexual partners. It is thus possible to locate these DCAs to which colonies in an area contribute drones and queens instead of locating all the nests these come from. DCAs can be located by observing the terrain or transecting it with a pheromone trap, which can then be used to samples drones (Williams, 1987). Using genetic tools, it is then possible to genotype the drones and infer the genotype of their mothers. Because drones are produced parthenogenetically and only carry alleles from their mother, genotyping drones allows for their easy assignment to specific queens. Similarly, by genotyping workers of a single queen, it is also possible to deduce the genotype of the queen and that of her mates (honey bee queens mate with many haploid drones). Since honey bee colonies are headed by a single queen, obtaining the number of queens in an area equals counting the number of colonies in this area (Baudry et al., 1998; Jaffé et al., 2009a). A recent model verified the validity of using locally mated queens to estimate colony densities based on the genotype of their brood. They conclude that at least 10 mated queens are needed to detect order of magnitude differences in colony density estimates (Arundel et al., 2012).