Grooming Behavior in Naturally Varroa-Resistant Apis mellifera Colonies From North-Central Argentina

RUSSO, ROMINA M.; LIENDO, MARIA C.; LANDI, LUCAS; PIETRONAVE, HERNÁN; MERKE, JULIETA; FAIN, HERNÁN; MUNTAABSKI, IRINA; PALACIO, MARIA A.; RODRÍGUEZ, GRACIELA A.; LANZAVECCHIA, SILVIA B.; SCANNAPIECO, ALEJANDRA C.

Frontiers in Ecology and Evolution

Frontiers Media SA

Año: 2020 vol. 8

The Western honey bee, Apis mellifera, is an important species in providing honeyand pollination services globally. The mite Varroa destructor is the major threat toA. mellifera, and it is associated with the severe colony winter mortality reported inrecent decades. However, Varroa mite tolerant or resistant populations of A. melliferahave been detected around the world. A proposed mechanism responsible for limitingmite population growth in the colonies is grooming behavior, the physical removal andinjury of mites from the adult bee bodies by individual workers or by their nest-mates.This behavioral strategy has been poorly studied in V. destructor-resistant coloniesworldwide, especially in honey bee populations of European origin. In Argentina, honeybee stocks showing survival without mite treatment have been reported. In the presentstudy, European-derived A. mellifera populations established in the Transition Chacoeco-region (Santa Fe province), with a subtropical climate, were characterized at thecolony level. A honey bee stock showing natural Varroa-resistance (M) was comparedto a Varroa-susceptible stock (C) for parameters of colony status (colony strength,percentage of Varroa infestation in adults and brood, hygienic behavior) and for indirectmeasures of grooming (percentage of fallen mites and damaged mites). M coloniesshowed lower phoretic and brood infestation and higher hygienic behavior in earlyautumn, and higher survival and population strength after wintering, in comparison withC colonies. The mean percentages of fallen mites and of damaged mites, and the injuryto mites were higher in M than in C colonies. Our results suggest that, by modulatingthe parasitization dynamics in colonies, grooming behavior would be associated withthe higher survival of Varroa-resistant stock. This study sheds light on how honey beecolonies can adaptively respond to mite pressure by modeling their behavior to resistVarroosis and provides evidence for grooming as an emerging factor evolving by natural selection. Percentage of damaged mites appears to be a reliable measure to enhancethis behavior in honey bee colonies by selective breeding. Finally, the importance ofimproving and protecting locally adapted honey bee populations with natural Varroaresistance for regional apiculture is discussed.