Summary
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 genie sex determination, can be maintained for 20 generations of random mating and top crossing in closed populations of at least 50 breeder queens.