title: Resistance rather than tolerance explains survival of savannah honeybees (Apis mellifera scutellata) to infestation by the parasitic mite Varroa destructor.
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.
authors.affiliation: Department of Zoology and Entomology,Social Insect Research Group,University of Pretoria,Private Bag X20,Hatfield,Pretoria 0028,South Africa.
authors.forename: Ursula
authors.initials: U
authors.lastname: Strauss
authors.affiliation: Department of Zoology and Entomology,Social Insect Research Group,University of Pretoria,Private Bag X20,Hatfield,Pretoria 0028,South Africa.
authors.forename: Vincent
authors.initials: V
authors.lastname: Dietemann
authors.affiliation: Department of Zoology and Entomology,Social Insect Research Group,University of Pretoria,Private Bag X20,Hatfield,Pretoria 0028,South Africa.
authors.forename: Hannelie
authors.initials: H
authors.lastname: Human
authors.affiliation: Department of Zoology and Entomology,Social Insect Research Group,University of Pretoria,Private Bag X20,Hatfield,Pretoria 0028,South Africa.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Crewe
authors.affiliation: Department of Zoology and Entomology,Social Insect Research Group,University of Pretoria,Private Bag X20,Hatfield,Pretoria 0028,South Africa.
authors.forename: Christian W W
authors.initials: CW
authors.lastname: Pirk
mesh_terms: D000818:Animals; D001516:Bees / Q000469:parasitology*; D001947:Breeding; D006790:Host-Parasite Interactions; D012098:Reproduction / Q000502:physiology; D012641:Selection, Genetic; D057077:Varroidae / Q000502:physiology*
keywords: Apis mellifera scutellata; Varroa destructor; mite; physiological cost; reproduction; resistance; tolerance