The payoffs and tradeoffs of hygienic behavior: A large-scale field study on a local population of honey bees
Honey bees (Apis mellifera) are exposed to a variety of risk factors, but the ectoparasitic mite Varroa destructor and its associated viruses are considered to be the most significant problem worldwide. It has been widely recognized that honey bee stocks resistant to the mites are an essential part of any sustainable long-term management of Varroa. The aim of this study was to evaluate the efficacy of hygienic behavior in a local population of honey bees in order to reduce Varroa infestation. A bi-directional selection for high and low rates of hygienic behavior was carried out in Israel using either queen artificially inseminated or naturally mated. Colonies were screened for performance: population size, honey production, control of Varroa infestation, and the level of hygienic behavior. Furthermore, we examined the costs and benefits of selection using measurements of colony performance. Either way, selected lines should be tested for trade-offs and benefits to ensure their productivity. The selection process revealed that the trait is heritable. Maternal phenotype has a significant effect on Varroa load, as colonies founded by hygienic daughter queens showed a significantly lower parasite load. No major trade-offs were found between the rate of hygienic behavior, honey yield, and population size. Measuring the direct benefits of hygienic behavior through colony performance suggests that breeding for this trait makes bees more resistant to Varroa destructor. These results are promising for our successful local bee breeding programs in a Mediterranean climate.