DOI: 10.25338/b8864j
title: Bee-associated fungi mediate effects of fungicides on bumble bees

description: Bumble bees are important pollinators that face threats from multiple
 sources, including agrochemical application. Declining bumble bee
 populations have been linked to fungicide application, which could
 directly affect the fungi often found in the stored food and
 gastrointestinal (GI) tract of healthy bumble bees. We test the hypothesis
 that fungicides impact bee health by disrupting bee–fungi interactions. We
 examined the interactive effects of the fungicide propiconazole and fungal
 supplementation on the survival, reproduction and microbiome composition
 of microcolonies (queenless colonies) using two species, Bombus
 vosnesenskii and B. impatiens. We found that
 in B. vosnesenskii, fungicide exposure decreased survival, while
 fungal supplementation mitigated fungicide effects. For B.
 impatiens, fungicide application had no effect, but fungal supplementation
 improved survival and offspring production. Fungicides reduced fungal
 abundance in B. vosnesenskii microcolonies, but not
 in B. impatiens, where instead fungal addition decreased fungal
 abundance (ITS copy number). Fungal composition varied between treatments
 but differently between bee species. In B. impatiens, fungal
 addition increased microbiome diversity. In B. vosnesenskii, the
 abundance of the pathogen Ascosphaera was negatively
 associated with survival, while the
 yeast Zygosaccharomyces was positively associated with
 survival. Our results highlight that bumble bee species differ in response
 to fungicides and in the nature of bee‐fungi associations. Fungicides can
 alter bee–fungi interactions with consequences for bee survival and
 reproduction, and exploring the mechanisms of such interactions, including
 interactions among fungi in the bee GI tract, may offer insights into
 bumble bee biology and conservation strategies.
description: For full methodology please see the manuscript associated with
 these data. Microcolonies (queen-less colonies) of two
 species of bumble bee (<em>Bombus vosnesenskii </em>and
 <em>B. impatiens</em>) were exposed to either nectar
 containing the fungicide propiconazole or control nectar for one week.
 After this, they were either given a collection of bee-associated fungi in
 their nectar, or given control nectar for the following 2-3 weeks.
 Microcolony survival over time was measured, as was consumption of both
 fungicide-treated nectar and fungi-treated nectar. For <em>B.
 impatiens</em>, offspring production was quantified.
 Following microcolony termination, workers from each microcolony
 were dissected to remove the gut, which was separated into two sections
 (crop and midgut+hindgut). Three samples were pooled for each microcolony
 and DNA was then extracted from each sample. Samples from colonies that
 microcolonies were sourced from were included in processing and analysis,
 as were pollen samples. These samples were sent for amplicon sequencing of
 the 16S and ITS regions to determine bacterial and fungal gut community
 composition (sequences available on the NCBI SRA - BioProject:
 PRJNA759617). Total fungal gut abundance was quantified using qPCR.
 Sequences were processed using DADA2, and were then arranged into phyloseq
 objects for community analyses.
description: Refer to the ReadMe files for information on the included data
 and script files. microcolony_ReadMe.txt provides
 details on the microcolony response datasets.
 sequences_ReadMe.txt provides information on how to access raw
 sequences and on sample data associated with 16S and ITS phyloseq
 objects. Script_ReadMe.txt provides information on the
 R scripts used to analyze data associated with this project.