Abstract:
Varroa destructor is considered the most damaging parasite affecting honeybees (Apis mellifera L.). However, some honeybee
populations such as the savannah honeybee (Apis mellifera scutellata) can survive mite infestation without treatment.
It is unclear if survival is due to resistance mechanisms decreasing parasite reproduction or to tolerance mechanisms decreasing
the detrimental effects of mites on the host. This study investigates both aspects by quantifying the reproductive
output of V. destructor and its physiological costs at the individual host level. Costs measured were not consistently
lower when compared with susceptible honeybee populations, indicating a lack of tolerance. In contrast, reproduction
of V. destructor mites was distinctly lower than in susceptible populations. There was higher proportion of infertile individuals
and the reproductive success of fertile mites was lower than measured to date, even in surviving populations. Our
results suggest that survival of savannah honeybees is based on resistance rather than tolerance to this parasite. We identified
traits that may be useful for breeding programmes aimed at increasing the survival of susceptible populations.
African honeybees may have benefited from a lack of human interference, allowing natural selection to shape a population
of honeybees that is more resistant to Varroa mite infestation.
