Signatures of adaptive decreased virulence of deformed wing virus in an isolated population of wild honey bees (Apis mellifera)

Abstract

AbstractUnderstanding the ecological and evolutionary processes that drive host-pathogen interactions is critical for combating epidemics and conserving species. TheVarroa destructormite and deformed wing virus (DWV) are two synergistic threats to Western honey bee (Apis mellifera) populations across the globe. Distinct honey bee populations have been found to self-sustain despiteVarroainfestations, including colonies within the Arnot Forest outside Ithaca, NY, USA. We hypothesized that in these honey bee populations, DWV has been selected to produce an avirulent infection phenotype, allowing for the persistence of both host and disease-causing agents. To investigate this, we assessed the presence and titer of viruses in bees from the Arnot Forest and managed apiaries, and assessed genomic variation and virulence differences between DWV isolates. Across groups, we found viral abundance was similar, but viral genotypes were distinct. We also found that infections with viral isolates from the Arnot Forest resulted in higher survival and lower rates of symptomatic deformed wings, compared to analogous isolates from managed colonies, providing preliminary evidence to support the hypothesis of adaptive decreased viral virulence. Overall, this multi-level investigation of virus genotype and phenotype across different contexts reveals critical insight into global bee health and the ecological and evolutionary processes that drive host-pathogen interactions.