The current worldwide pollinator decline is caused by the interplay of different drivers. Several strategies have been undertaken to counteract or halt this decline, one of which is the implementation of wildflower fields. These supplementary flowers provide extra food resources and have proven their success in increasing pollinator biodiversity and abundance. Yet such landscape alterations could also alter the host–pathogen dynamics of pollinators, which could affect the populations. In this study, we investigated the influence of sown wildflower fields on the prevalence of micro-parasites and viruses in the wild bumble bee Bombus pascuorum, one of the most abundant bumble bee species in Europe and the Netherlands. We found that the effect of sown wildflower fields on micro-parasite prevalence is affected by the composition of the surrounding landscape and the size of the flower field. The prevalence of micro-parasites increases with increasing size of sown wildflower fields in landscapes with few semi-natural landscape elements. This effect was not observed in landscapes with a high amount of semi-natural landscape elements. We elaborate on two mechanisms which can support these findings: (1) “transmission hot spots” within the altered flower-networks, which could negatively impact hosts experiencing an increased exposure; (2) improved tolerance of the hosts, withstanding higher parasite populations.
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This project was supported in part by the Ghent University and the Research Foundation-Flanders (FWO-Vlaanderen) for the Belgian team, and the team in the Netherlands by the Netherlands Organization for Scientific Research (NWO-ALW; Biodiversity Works Program, 841.11.001) and Syngenta. D.K. was additionally supported by EC FP7 project LIBERATION (311781; www.fp7liberation.eu) and EC COST Action SUPER-B (FA1307; http://www.superb-project.eu). We also thank Dr. Tibor Bukovinszky for his assistance.
Author contribution statement
DK, GS and IM conceived the ideas and designed methodology; NP and TL collected the data; NP, IM and JS analyzed the data; NP and IM led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.
Compliance with ethical standards
Conflict of interest
The authors declare that there is no conflict of interest.
The data will be made publicly available at Dryad.
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