Bee Preference for Native versus Exotic Plants in Restored Agricultural Hedgerows
Summary (2 min read)
Introduction
- Intensive agricultural systems often are lacking in native pollinators (Winfree et al. 2009) and hence native pollination services to crops (Kremen et al.
- Often, non-native annual plants are recommended for pest-control enhancement on farm sites, despite the fact that native plants are more suitable for conservation efforts that intend to also preserve native plants and the beneficial insects associated with them (see Tuell et al. 2008 and references therein).
Methods
- Hedgerow Sites and Plantings Newly established hedgerow sites were planted between 2007 and 2008 for the purpose of enhancing native bee populations.
- As the collector slowly walked along the hedgerow, they checked every flower for the presence of a bee.
- Therefore for new hedgerow sites, there were four sites and three sample rounds, resulting in 12 records for native plants and 12 for exotic plants and at mature hedgerow sites there were four sites and four sample rounds, resulting in 16 records each for native and exotic plants.
- The authors included sample round nested within site as a repeated factor, site as a random factor, and floral cover as the covariate.
- For bee abundance on native and exotic plants, standardizing for floral cover of natives and exotics additionally gives a measure of “preference” (Johnson 1980).
Results
- At new hedgerow sites, regression slopes were significantly different for native bee abundance on native versus exotic plants (floral cover by plant type interaction: F[1,11] = 10.64, p = 0.008).
- Native Species Ranking Semi-quantitative ranking of preference among native plant species showed that when present, Eriogonum fasciculatum and Salvia spp. were the most preferred native plant species (Table 1).
- Large numbers of syrphid flies (Family Syrphidae), which also can be important native pollinators of agricultural crops (Jauker & Wolters 2008), were caught on elderberry (L. Morandin & C. Kremen, unpublished data).
Discussion
- These data indicate that native bees prefer to forage on native plants in both new and mature hedgerow sites.
- At new hedgerow sites where native plants were sparse, substantial proportions of native bee (45%) and honey bee (66%) collections were on exotic plants.
- Returning honey bee foragers communicate information regarding location and floral odor of rewarding patches to the hive (Arenas et al. 2007).
- As native plants generally had low amounts of floral display at new hedgerow sites, there likely would be little recruitment to these plant species.
- In light of the recent serious declines of honey bees and suspected role of poor nutrition in agricultural settings (vanEngelsdorp et al. 2009), creation of native plant hedgerows in intense agricultural areas may benefit honey bee colony health.
1 2 SALVI HEAR5,
- ACMI2, Achillea millefolium; ASFA, Asclepias fascicularis; ATLE, Atriplex lentiformis; CEGR2, Ceanothus griseus; EPCA4, Epilobium californicum; ERFA2, Eriogonum fasciculatum; ESCA2, Eschscholzia californica; FRCA6, Fremontodendron californicum; GRCA, Grindelia camporum; HEAR5, Heteromeles arbutifolia; PHCA, Phacelia californica; RHCA, Rhamnus californica; ROCA2, Rosa californica; SALVI, Salvia spp.; SAME5, Sambucus mexicana.
- Plants with the highest value relative to other plants at each site and sample round were ranked as “1,” the next highest value was ranked as “2,” etc. et al. 2009; Garibaldi et al. 2011).
- Recommendations for hedgerow plantings to promote pollinators often stress the use of a range of plant species in order to provide diverse and continuous resources throughout the season (Menz et al. 2011).
- Most of the reviewed studies were conducted in the EU on Bombus species.
- In addition, these data indicate that hedgerows of mature native plants will attract or promote a more species rich and diverse community of native bees than field edges where exotic plants dominate, possibly aiding stability of pollination function.
Acknowledgments
- The authors thank the growers and land owners in Yolo County, CA, that allowed us to work on their property.
- The research was funded by an NSERC Postdoctoral Fellowship to L.A.M., a Conservation Innovation Grant, a National Science Foundation grant, and a National Geographic Society Research and 6 Restoration Ecology Exploration grant.
- Members of the Kremen Laboratory, UC Berkeley, provided valuable comments on manuscript drafts.
LITERATURE CITED
- The global stock of domesticated honey bees is growing slower than agricultural demand for pollination.
- The area requirements of an ecosystem service: crop pollination by native bee communities in California.
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Citations
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Cites background or result from "Bee Preference for Native versus Ex..."
...…earlier findings that mature hedgerows (i.e., .10 years old) enhance abundances in adjacent fields, rather than dilute them through concentration (Morandin and Kremen 2013b) That these restorations could eventually even act as source populations into other parts of the landscape is an important…...
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...Plantings may also create nesting habitat and function as refuges from pesticides and soil disturbances such as tilling (Morandin and Kremen 2013a, b)....
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...…that included both the data collected in this study and additional data from sites where we collected flower visitors with identical methods (Morandin and Kremen 2013a, b; C. Kremen, unpublished data), we quantified each pollinator species’ level of floral resource specialization by…...
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...…are at risk from pesticides (Brittain et al. 2010) and habitat loss (Kennedy et al. 2013), multiple studies have shown that increasing vegetative diversity locally boosts pollinator species richness and abundance (e.g., Kohler et al. 2008, Kennedy et al. 2013, Morandin and Kremen 2013a)....
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Cites background from "Bee Preference for Native versus Ex..."
...The biodiversity supported by hedgerows influences the provision of pest regulation (Morandin et al., 2014) and pollination services (Morandin and Kremen, 2013b; Morandin et al., 2016), essential for agricultural productivity (Natural England, 2012)....
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...An established shrub layer can provide important forage for Apoidea (bees) and other pollinator species (Hannon and Sisk, 2009), especially where the abundance and diversity of floral resources has been enhanced by management (Morandin and Kremen, 2013a)....
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...For instance, pollinators were found to favour hedgerows with native species over introduced species in a California based study (Morandin and Kremen, 2013a)....
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References
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...For bee abundance on native and exotic plants, standardizing for floral cover of natives and exotics additionally gives a measure of “preference” (Johnson 1980)....
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...Honey bees are eusocial and recruit foragers to rewarding patches (Winston 1987)....
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1,963 citations
"Bee Preference for Native versus Ex..." refers background in this paper
...Honey bees are eusocial and recruit foragers to rewarding patches (Winston 1987)....
[...]
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"Bee Preference for Native versus Ex..." refers background in this paper
...If the interaction was significant, we kept the interaction term and report least squares mean difference and the region(s) of significance between native and exotic plants along values of the covariate, flower cover (Johnson & Neyman 1936; Milliken & Johnson 2002)....
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Frequently Asked Questions (15)
Q2. How much of the leading food crops are dependent on pollinators?
Seventy-five percent of the leading food crops and 35% of global food production is dependent on pollinators (Klein et al. 2007).
Q3. Why are native plants essential to maintaining bee diversity?
Because a quarter of native bee species that had greater than two individuals collected at these sites were found on only one native plant species, and each on a different native plantspecies, their data suggest that a diversity of native plants is essential to maintaining native bee diversity.
Q4. How many bee species were found on one species of native plant?
Of the native bee species that were represented by greater than two individuals (17 species), four bee species were found on only one species of native plant in this subset of samples.
Q5. What was the funding for this research?
The research was funded by an NSERC Postdoctoral Fellowship to L.A.M., a Conservation Innovation Grant, a National Science Foundation grant, and a National Geographic Society Research and6 Restoration EcologyExploration grant.
Q6. What is the role of native plants in honey bee colony health?
In light of the recent serious declines of honey bees and suspected role of poor nutrition in agricultural settings (vanEngelsdorp et al. 2009), creation of native plant hedgerows in intense agricultural areas may benefit honey bee colony health.
Q7. What is the effect of a greater bee diversity on native plants?
Recent studies suggest that habitats with greater bee diversity can result in greater or more stabilized crop production (Klein et al.
Q8. Why did the composition of the hedgerows differ between sites?
Composition varied among sites in native plants due to differences in service focus (pollination enhancement at new hedgerows, pest control at mature hedgerows), differencesin species choices made by the land owner, and differential survival among sites.
Q9. How many species of bees were observed at mature hedgerow sites?
Bee Abundance, Richness, and DiversityOf the 23 species of native bees netted on flowers at the new hedgerow sites, 7 species were observed only on exotic plants and 7 species were observed only on native plants.
Q10. What are the important resources for enhancing native bee abundance and diversity in degraded?
Native plants within these small, linear habitat elements are the most important resource for enhancing native bee abundance and diversity in degraded landscapes.
Q11. What did the researchers find to be the important resource for honey bees?
Honey bees in new hedgerow sites did not prefer native plants but rather used native and exotic plants in proportion to their abundance.
Q12. What is the significance of native plant hedgerows?
native plant hedgerows, by enhancing bee diversity over exotic weedy edges, may help to stabilize or enhance crop production.
Q13. What is the effect of native plants on bees?
In addition, these data indicate that hedgerows of mature native plants will attract or promote a more species rich and diverse community of native bees than field edges where exotic plants dominate, possibly aiding stability of pollination function.
Q14. What is the preference of native bees at mature hedgerow sites?
Native bees preferred native plants over exotic plants at mature hedgerow sites at all cover amounts (F[1,13] = 39.08, p < 0.0001) (Fig. 3).
Q15. How many bee species were found on native plants?
The authors found significantly more native bees on native plants than exotic plants (t[17] = −3.32, p = 0.004; Fig. 1) and p < 0.05 for all floral cover values greater than 15.