Population Genetic Studies on Sex Alleles in the Honeybee Using the Example of the Kangaroo Island Bee Sanctuary

Abstract

SummaryThe common practice of crossing different races of honeybees has created a demand for the establishment of isolated reserves for pure ecotypes of the main races. On Kangaroo Island, S. Australia, a bee sanctuary 100 years old, the average survival rate of brood was found to be 75.6%. Mortality of 6.5% was caused by factors other than sex alleles, so the survival rate resulting from sex alleles was 82.1%.Equations are presented for calculation of survival rate of brood (S) in populations in equilibrium, S = (N-1)/N, and in unstable populations, S-1-pf pm-qfqm-rfrm…. Equations are developed for calculating the frequencies of sex alleles in subsequent generations, and after the introduction of new alleles (and new queens), and also differences between the frequencies of sex alleles in the two sexes.In natural selection, sex alleles in honeybees represent an example of overdominance, with total elimination of all homozygotes in populations with multiple alleles and different frequencies of those alleles in the sexes.Calculations show that 36% of the drones that mated with the queens in the sanctuary carried the same sex alleles as the queens.Only 6 of 12 sex alleles known to occur in the honeybee were present among the bees in the sanctuary. An increase in the number of alleles above 8–10 in a population gives very little improvement in the percentage of surviving larvae. Theoretical calculations shows that the frequencies of different sex alleles must be equal throughout the bee population on Kangaroo Island. When a new allele is introduced into a population with few alleles, even in a very low proportion, its frequency increases rapidly, and thus the survival of brood increases. The maximum survival rate of brood in a population is reached when the sex alleles are in equilibrium. Before reaching equilibrium for different sex alleles, any generation of queens produces virgins and drones with different frequencies of these alleles. When there are few alleles, there is a diminishing oscillation in the frequency of the same sex allele between the two sexes, in subsequent generations. The best way to increase the number of sex alleles in a population and to increase the survival of brood, with a minimal change of other characters, is to introduce one or very few queens inseminated by several (not many) different drones.Although the survival rate of brood on Kangaroo Island was rather low, after 100 years of isolation, the colonies were still good honey producers.