DISCUSSION

In this study we investigated changes in the bumble bee virome under field conditions in relation to habitat composition and configuration. Our results show that viral loads and viral richness increased after field exposure and shifted from an initial dominance of honey bee associated viruses to a higher virus richness in the colonies at the end of the experiment, including several different bumble bee viruses. The spatial structure of the surrounding landscape was related to the changes in viral patterns at fine spatial scales, with habitat Shannon diversity being positively linked to lower virus richness and appearance of new viruses, while well-connected agricultural patches decreased the viral load. Colony development parameters were not directly negatively affected by viruses but were influenced by the same landscape parameters that drove virus prevalence. Our results emphasize the importance of landscape heterogeneity and connectivity for wild pollinator health .