Closed population honeybee breeding 4. The distribution of sex alleles with top crossing

Computer simulation was used to investigate the efficacy of top crossing within closed breeding populations of honeybees. Top crossing is carried out by selecting a single breeder queen (top-cross parent) to contribute all or a significant proportion of the drones needed to inseminate the virgin queens of a closed population. Different population-genetic models were tested by varying the number of queens selected as breeders, the source and relative contribution of the selected top--cross parent and the method of queen replacement each generation. It was demonstrated that acceptable levels of brood viability, as a consequence of genic sex determination, can be maintained for 20 generations of random mating and top crossing in closed populations of at least 50 breeder queens.