CONCLUSIONS
This study highlights that even though commercially raised bumble bees
typically carry several honey bee viruses, the viral composition
generally changes towards bumble bee viruses after field exposure, with
no or little impact on colony development. Hence, the widely studied and
discussed negative impacts of honey bee virus transmissions to wild
pollinators might often be negligible for B. terrestris since
neither a coherent establishment of such viruses in the colonies during
field exposure nor clear consequences on colony development were found.
Additionally, our results highlight the importance of landscape
structure in shaping viral patterns during field exposure. Notably,
habitat heterogeneity and well-connected agricultural patches in areas
with little forest cover led to lower viral loads, fewer viruses, and
lower appearance of new viruses in bumble bee colonies. We thus
highlight the importance of habitat diversity and heterogeneity in
agricultural landscapes, as evidenced numerous times before underline
the importance of maintaining existing heterogeneous agricultural
landscapes and restoring where necessary.