The role of disease in bee foraging ecology

Koch, Hauke; Brown, Mark J. F.; Stevenson, Philip C.

doi:10.1016/j.cois.2017.05.008

Cited by 80 publications

(70 citation statements)

References 67 publications

(102 reference statements)

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“…Flowers can be visited by a wide range of pollinators and other species (McArt et al 2014) and are logical suspects as hotspots of pathogen transmission among bees, but very little empirical work has addressed this (reviewed in Koch et al 2017). More than 20 yr ago, a landmark study showed that Bombus terrestris could become infected with Crithidia by foraging on inflorescences previously foraged on by infected bees (Durrer and Schmid-Hempel 1994).…”

Section: Introductionmentioning

confidence: 99%

Disease where you dine: plant species and floral traits associated with pathogen transmission in bumble bees

Adler

Michaud

Ellner

et al. 2018

Ecology

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Hotspots of disease transmission can strongly influence pathogen spread. Bee pathogens may be transmitted via shared floral use, but the role of plant species and floral trait variation in shaping transmission dynamics is almost entirely unexplored. Given the importance of pathogens for the decline of several bee species, understanding whether and how plant species and floral traits affect transmission could give us important tools for predicting which plant species may be hotspots for disease spread. We assessed variation in transmission via susceptibility (probability of infection) and mean intensity (cell count of infected bees) of the trypanosomatid gut pathogen Crithidia bombi to uninfected Bombus impatiens workers foraging on 14 plant species, and assessed the role of floral traits, bee size and foraging behavior on transmission. We also conducted a manipulative experiment to determine how the number of open flowers affected transmission on three plant species, Penstemon digitalis, Monarda didyma, and Lythrum salicaria. Plant species differed fourfold in the overall mean abundance of Crithidia in foraging bumble bees (mean including infected and uninfected bees). Across plant species, bee susceptibility and mean intensity increased with the number of reproductive structures per inflorescence (buds, flowers and fruits); smaller bees and those that foraged longer were also more susceptible. Trait-based models were as good or better than species-based models at predicting susceptibility and mean intensity based on AIC values. Surprisingly, floral size and morphology did not significantly predict transmission across species. In the manipulative experiment, more open flowers increased mean pathogen abundance fourfold in Monarda, but had no effect in the other two plant species. Our results suggest that variation among plant species, through their influence on pathogen transmission, may shape bee disease dynamics. Given widespread investment in pollinator-friendly plantings to support pollinators, understanding how plant species affect disease transmission is important for recommending plant species that optimize pollinator health.

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Section: Introductionmentioning

confidence: 99%

Disease where you dine: plant species and floral traits associated with pathogen transmission in bumble bees

Adler

Michaud

Ellner

et al. 2018

Ecology

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“…In particular, consuming the alkaloids nicotine and anabasine, found in Solanaceous plants, reduced infection by the gut pathogen Crithidia in the bumble bee Bombus impatiens at ecologically relevant concentrations (Richardson et al 2015). Given that some bee species have declined in recent years, due in part to pathogens (Potts et al 2010), and the largely unknown role of floral traits in pollinator-pathogen dynamics (McArt et al 2014, Koch et al 2017, it is critical to explore factors that influence flower-bee-pathogen interactions. Given that some bee species have declined in recent years, due in part to pathogens (Potts et al 2010), and the largely unknown role of floral traits in pollinator-pathogen dynamics (McArt et al 2014, Koch et al 2017, it is critical to explore factors that influence flower-bee-pathogen interactions.…”

Section: Introductionmentioning

confidence: 99%

From plant fungi to bee parasites: mycorrhizae and soil nutrients shape floral chemistry and bee pathogens

Davis

Aguirre

Barber

et al. 2019

Ecology

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Bee populations have experienced declines in recent years, due in part to increased disease incidence. Multiple factors influence bee-pathogen interactions, including nectar and pollen quality and secondary metabolites. However, we lack an understanding of how plant interactions with their environment shape bee diet quality. We examined how plant interactions with the belowground environment alter floral rewards and, in turn, bee-pathogen interactions. Soil-dwelling mycorrhizal fungi are considered plant mutualists, although the outcome of the relationship depends on environmental conditions such as nutrients. In a 2 9 2 factorial design, we asked whether mycorrhizal fungi and nutrients affect concentrations of nectar and pollen alkaloids (anabasine and nicotine) previously shown to reduce infection by the gut pathogen Crithidia in the native bumble bee Bombus impatiens. To ask how plant interactions affect this common bee pathogen, we fed pollen and nectar from our treatment plants, and from a wildflower pollen control with artificial nectar, to bees infected with Crithidia. Mycorrhizal fungi and fertilizer both influenced flowering phenology and floral chemistry. While we found no anabasine or nicotine in nectar, high fertilizer increased anabasine and nicotine in pollen. Arbuscular mycorrhizal fungi (AMF) decreased nicotine concentrations, but the reduction due to AMF was stronger in high than low-nutrient conditions. AMF and nutrients also had interactive effects on bee pathogens via changes in nectar and pollen. High fertilizer reduced Crithidia cell counts relative to low fertilizer in AMF plants, but increased Crithidia in non-AMF plants. These results did not correspond with effects of fertilizer and AMF on pollen alkaloid concentrations, suggesting that other components of pollen or nectar were affected by treatments and shaped pathogen counts. Our results indicate that soil biotic and abiotic environment can alter bee-pathogen interactions via changes in floral rewards, and underscore the importance of integrative studies to predict disease dynamics and ecological outcomes.

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“…Wild B. terrestris colonies infected with C. bombi are less likely to produce new daughter queens compared with uninfected colonies (Goulson et al, 2017). Crithidia infection reduced queen colony founding success and colony size (Brown et al, 2003), and reduced motor learning rates of flower handling in B. impatiens (Gegear et al, 2005), which could influence how effectively bumble bees pollinate and forage (Koch et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Effect of timing and exposure of sunflower pollen on a common gut pathogen of bumble bees

LoCascio

Pasquale

Amponsah

et al. 2019

Ecological Entomology

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1. Several bee species are declining due to multiple factors, including pathogens. Ingestion of sunflower (Helianthus annuus) pollen can dramatically reduce the bumble bee gut pathogen Crithidia bombi, but little is known about how timing and exposure to sunflower pollen consumption affects pathogen load.2. Two experiments were carried out to investigate how exposure to sunflower pollen relative to pathogen exposure affects Crithidia bombi in Bombus impatiens. Foraging trials with pollen-producing and male-sterile (pollen absent) sunflower lines were performed to investigate whether sunflower pollen affected pathogen transmission in a single foraging bout, and 7-day laboratory trials were done to investigate whether timing and duration of exposure to sunflower pollen after infection affected C. bombi.3. In foraging trials, pollen presence on inflorescences inoculated with C. bombi did not affect transmission (pathogen cell counts of foraging workers) 1 week later, suggesting that a brief experience with sunflower pollen concurrent with pathogen exposure is insufficient to reduce infection. In laboratory trials, consuming sunflower pollen for the first 3.5 days or all 7 days after infection reduced cell counts compared with a negative control pollen, but consuming sunflower pollen starting 3.5 days after infection did not. Consuming sunflower pollen for 7 days was significantly and substantially more effective than any other treatment. Thus, both duration and timing of exposure to sunflower pollen may affect pathogen load.4. These results are important for understanding ecological disease dynamics in natural settings with free-flying bumble bees, and may inform decisions about using medicinal diets to manage bumble bee health commercially.

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The role of disease in bee foraging ecology

Cited by 80 publications

References 67 publications

Disease where you dine: plant species and floral traits associated with pathogen transmission in bumble bees

Disease where you dine: plant species and floral traits associated with pathogen transmission in bumble bees

From plant fungi to bee parasites: mycorrhizae and soil nutrients shape floral chemistry and bee pathogens

Effect of timing and exposure of sunflower pollen on a common gut pathogen of bumble bees

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