Genetic diversity affects colony survivorship in commercial honey bee colonies

Abstract

Honey bee (Apis mellifera) queens mate with unusually high numbers of males (average of approximately 12 drones), although there is much variation among queens. One main consequence of such extreme polyandry is an increased diversity of worker genotypes within a colony, which has been shown empirically to confer significant adaptive advantages that result in higher colony productivity and survival. Moreover, honey bees are the primary insect pollinators used in modern commercial production agriculture, and their populations have been in decline worldwide. Here, we compare the mating frequencies of queens, and therefore, intracolony genetic diversity, in three commercial beekeeping operations to determine how they correlate with various measures of colony health and productivity, particularly the likelihood of queen supersedure and colony survival in functional, intensively managed beehives. We found the average effective paternity frequency (m e ) of this population of honey bee queens to be 13.6 ± 6.76, which was not significantly different between colonies that superseded their queen and those that did not. However, colonies that were less genetically diverse (headed by queens with m e ≤ 7.0) were 2.86 times more likely to die by the end of the study when compared to colonies that were more genetically diverse (headed by queens with m e > 7.0). The stark contrast in colony survival based on increased genetic diversity suggests that there are important tangible benefits of increased queen mating number in managed honey bees, although the exact mechanism(s) that govern these benefits have not been fully elucidated.

Genetic diversity confers colony-level benefits due to individual immunity

“…Our findings support the idea that variance-based selection-whereby intercolony variance is reduced by multiple mating-may explain the evolution of polyandry in social insects [24]. Furthermore, based on previous theoretical and empirical data concerning the threshold mating frequency on the polyandry continuum of honeybees [24,25], our data are consistent with an effective paternity frequency of approximately 7 maximizing the effects of polyandry in this system. This is significantly lower than the average observed mating frequency for A. mellifera and lower than what is typically tested when attempting to determine if intracolonial genetic diversity influences behaviour and colony fitness [15,18].…”

Genetic characterization of the honeybee (Apis mellifera) population of Rodrigues Island, based on microsatellite and mitochondrial DNA

“…The reduction of genetic diversity due to beekeeping practices is one of the several causes suggested (Oldroyd 2007) and has had an important impact on managed colonies (De la Rúa et al 2013). Studies have demonstrated that reduced levels of intra-colonial genetic diversity affect colony fitness (Tarpy et al 2013).…”

Improving the future of honey bee breeding programs by employing recent scientific advances

“…Therefore, lack of genetic diversity within a colony due to poor queen mating success because of low queen quality or lack of healthy drones can disrupt colony homeostasis. This in turn could lead to economic losses due to beekeepers having to re-queen their colonies or ultimately colony loss [45,46]. As the mechanisms underlying the correlation between mating success and colony health are not fully understood, bee breeders can ensure the quality of reproductive castes only if these mechanisms are further elucidated.…”

“…The queen takes 1-5 mating flights during which she mates with an average of 12-14 drones [46] storing all the sperm she will use during her lifetime. After mating, queens undergo behavioral, physiological and transcriptional changes signaling their new role in the hive.…”