Abstract
Introduced species can have cascading effects on ecological communities, but indirect effects of species introductions are rarely the focus of ecological studies. For example, managed honey bees (Apis mellifera) have been widely introduced outside their native range and are increasingly dominant floral visitors. Multiple studies have documented how honey bees impact native bee communities through floral resource competition, but few have quantified how these competitive interactions indirectly affect pollination and plant reproduction. Such indirect effects are hard to detect because honey bees are themselves pollinators and may directly impact pollination through their own floral visits. The potentially huge but poorly understood impacts that non-native honey bees have on native plant populations combined with increased pressure from beekeepers to place hives in U.S. National Parks and Forests makes exploring impacts of honey bee introductions on native plant pollination of pressing concern. In this study, we used experimental hive additions, field observations, as well as single-visit and multiple-visit pollination effectiveness trials across multiple years to untangle the direct and indirect impacts of increasing honey bee abundance on the pollination of an ecologically important wildflower, Camassia quamash. We found compelling evidence that honey bee introductions indirectly decrease pollination by reducing nectar and pollen availability and competitively excluding visits from more effective native bees. In contrast, the direct impact of honey bee visits on pollination was negligible, and, if anything, negative. Honey bees were ineffective pollinators, and increasing visit quantity could not compensate for inferior visit quality. Indeed, although the effect was not statistically significant, increased honey bee visits had a marginally negative impact on seed production. Thus, honey bee introductions may erode longstanding plant-pollinator mutualisms, with negative consequences for plant reproduction. Our study calls for a more thorough understanding of the indirect effects of species introductions and more careful coordination of hive placements.
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Claims 7
Claim · model-written summary
Honey bee introductions indirectly decrease pollination of Camassia quamash by reducing nectar and pollen availability and by competitively excluding more effective native bees.
- Taxon
- Camassia quamash
Camassia quamashe2 - Treatment
- honey bee introductionse1
- Interactor
- Apis mellifera
_Apis_mellifera_(female)_-_on_viburnum_tinus_flowers.jpg?width=60)
Apis melliferae3pollinator - Outcome
- pollinatione1
- Direction
- decreasee1
- Qualifier
- by reducing nectar and pollen availability and competitively excluding visits from more effective native beese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_Apis_mellifera_(female)_-_on_viburnum_tinus_flowers.jpg?width=500)
Verbatim
e1“honey bee introductions indirectly decrease pollination by reducing nectar and pollen availability and competitively excluding visits from more effective native bees”
e2“an ecologically important wildflower, Camassia quamash”
e3“managed honey bees (Apis mellifera)”
Claim · model-written summary
The direct impact of honey bee visits on Camassia quamash pollination is negligible, and if anything negative.
- Taxon
- Camassia quamashCamassia quamashe2
- Treatment
- honey bee visitse1
- Outcome
- direct impact of honey bee visits on pollinatione1
- Direction
- no_changeinferrede1
- Qualifier
- if anything, negativee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the direct impact of honey bee visits on pollination was negligible, and, if anything, negative”
e2“an ecologically important wildflower, Camassia quamash”
Claim · model-written summary
Honey bees are ineffective pollinators of Camassia quamash.
- Taxon
- Camassia quamashCamassia quamashe2
- Interactor
- Apis melliferaApis melliferae3pollinator
- Outcome
- ineffective pollinatorse1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Honey bees were ineffective pollinators”
e2“an ecologically important wildflower, Camassia quamash”
e3“managed honey bees (Apis mellifera)”
Claim · model-written summary
Increasing honey bee visit quantity does not compensate for their inferior visit quality in Camassia quamash pollination.
- Taxon
- Camassia quamashCamassia quamashe2
- Outcome
- could not compensate for inferior visit qualitye1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“increasing visit quantity could not compensate for inferior visit quality”
e2“an ecologically important wildflower, Camassia quamash”
Claim · model-written summary
Increased honey bee visits had a marginally negative, non-significant impact on Camassia quamash seed production.
- Taxon
- Camassia quamashCamassia quamashe2
- Treatment
- increased honey bee visitse1
- Interactor
- Apis melliferaApis melliferae3pollinator
- Outcome
- seed productione1
- Direction
- negativee1
- Qualifier
- although the effect was not statistically significante1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“although the effect was not statistically significant, increased honey bee visits had a marginally negative impact on seed production”
e2“an ecologically important wildflower, Camassia quamash”
e3“managed honey bees (Apis mellifera)”
Claim · model-written summary
Honey bee introductions may erode longstanding plant-pollinator mutualisms with negative consequences for plant reproduction.
- Taxon
- Camassia quamashCamassia quamashe2
- Treatment
- honey bee introductionse1
- Outcome
- plant-pollinator mutualismse1
- Direction
- erodee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“honey bee introductions may erode longstanding plant-pollinator mutualisms, with negative consequences for plant reproduction”
e2“an ecologically important wildflower, Camassia quamash”
Claim · model-written summary
Hive placements should be coordinated more carefully to protect native Camassia quamash pollination.
- Taxon
- Camassia quamashCamassia quamashe2
- Outcome
- more careful coordination of hive placementse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“more careful coordination of hive placements”
e2“an ecologically important wildflower, Camassia quamash”