Covert deformed wing virus infections have long-term deleterious effects on honeybee foraging and survival.

Several studies have suggested that covert stressors can contribute to bee colony declines. Here we provide a novel case study and show using radiofrequency identification tracking technology that covert deformed wing virus (DWV) infections in adult honeybee workers seriously impact long-term foraging and survival under natural foraging conditions. In particular, our experiments show that adult workers injected with low doses of DWV experienced increased mortality rates, that DWV caused workers to start foraging at a premature age, and that the virus reduced the workers' total activity span as foragers. Altogether, these results demonstrate that covert DWV infections have strongly deleterious effects on honeybee foraging and survival. These results are consistent with previous studies that suggested DWV to be an important contributor to the ongoing bee declines in Europe and the USA. Overall, our study underlines the strong impact that covert pathogen infections can have on individual and group-level performance in bees.

Parent of origin gene expression in the bumblebee, Bombus terrestris, supports Haig's kinship theory for the evolution of genomic imprinting.

Genomic imprinting is the differential expression alleles in diploid individuals, with the expression being dependent on the sex of the parent from which it was inherited. Haig's kinship theory hypothesizes that genomic imprinting is due to an evolutionary conflict of interest between alleles from the mother and father. In social insects, it has been suggested that genomic imprinting should be widespread. One recent study identified parent-of-origin expression in honey bees and found evidence supporting the kinship theory. However, little is known about genomic imprinting in insects and multiple theoretical predictions must be tested to avoid single-study confirmation bias. We, therefore, tested for parent-of-origin expression in a primitively eusocial bee. We found equal numbers of maternally and paternally biased expressed genes. The most highly biased genes were maternally expressed, offering support for the kinship theory. We also found low conservation of potentially imprinted genes with the honey bee, suggesting rapid evolution of genomic imprinting in Hymenoptera.