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Native bees in agricultural pollination

Native bees in agricultural pollination

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Native bees in agricultural pollination

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  1. Native bees in agricultural pollination Neal Williams Department of Entomology, UC-Davis Laidlaw Bee Biology Facility ASI

  2. You will hear about . . . • A case study exploring the contributions of wild bees for crop pollination EAST versus WEST • A current projects : • Enhance floral resources to improve honey bee health and native bee populations • Modeling pollination services at the landscape scale a tool for conservation planning.

  3. Crop pollination • 35% of food production depends on animal pollinators (Klein et al. 2007) • Of 1300 crops worldwide, 70% require animal pollinators for one or more cultivars (Roubik 1995)

  4. Bees pollinate ~75% of crops(Nabhan and Buchmann 1997) Managed pollinators Native pollinators S. Greenleaf Apismelliferaon almondAnthophoraurbanaon tomato

  5. Challenges facing honeybees • Long term declines • 50% over 50 years changing demography of bee keeping • 1987 Varroa mites • 25% winter loss per year • 2006 Colony Collapse Disorder (CCD) • additional 20-35% loss Can native wild pollinators help? Are they already doing so?

  6. Non-Apis crop pollinators: mostly native bee species Wild populations Augochlora pura • Bees visiting crops and pollinating without active management of populations • Contributions under/un-measured until recently

  7. Ways of viewing pollination services Managed bees Wild bees Honey bees: Can honey bees fully pollinate? yes yes yes NO Honey bees Native bees other bees: Can other bees help pollinate? yes Managed bees Wild bees

  8. Value of pollination service Dependence Value Native bees Honeybee Pnb or Phb D V

  9. Contributions of native bees to crop pollination Claire Kremen UC Berkeley Rachael Winfree Rutgers University NJ Robbin Thorp -- UC Davis Sarah Greenleaf -- Princeton, CalState Sacramento

  10. Study questions: Pollination as ecosystem service • Can native pollinators provide adequate pollination? • How is pollination service affected by agricultural intensification • loss of natural habitat?  Landscape change • farm management?  Local habitat difference

  11. Two study systems New Jersey – Pennsylvania Yolo Co. California

  12. Watermelon, a good indicator crop for pollination service • Requires insect vector for pollen transfer • Flower open during one day • High pollen-deposition requirement (800 to 1400 grains to set fruit) • Visited by • 28 of 65 crop visitors in CA system • 45 species in PA-NJ system ♂ ♀

  13. Two study systems • Farm located along a landuse gradient • Near to natural habitat • Far Isolated from natural habitat Yolo Co. California Conventional near to semi-natural missing in the system

  14. Two study systems • Farms located along a landuse gradient • Farms within mostly semi natural • Farms in extensive agriculture • Organic Conventional • Natural • pesticide • pesticide • All small scale farms • All multiple crops • No differences in weedy plant • Abundance or Diversity New Jersey – Pennsylvania

  15. Landscape attributes

  16. Measuring pollination • Amount of pollen deposited per visit by each bee species • Number of visits to a flowerby each bee species

  17. California results Pollination by wild bees F2,11=6.85, r2=0.55, P = 0.01 * Pollination by native bees Pollen grains per flower ns ORG, NEAR ORG, FAR CONV, FAR Sufficient deposition 80% 50% 0% G=5.9, df =2, p=0.05

  18. California results Pollination by honey bees Grains deposited per flower-day ORG, NEAR ORG, FAR CON, FAR F1,12 = 2.07, r2adj=0.14, p = 0.17 2001 full-days

  19. Pennsylvania results Deposition among bee species Pollen grains deposited per visit Winfree, Williams et al. 2008

  20. Pennsylvania results Pollination by wild bees alone is sufficient at > 90% of farms FAR NEAR Farm types pollination Conventional Organic Pollination threshold % Semi-natural habitat

  21. Summary of pollination results Sufficient pollination of watermelon • Native bees 91% of farms • Honeybee 78% of farms

  22. Summary of comparison

  23. Landscape attributes

  24. Summary and Implications • Native bees can provide significant pollination for crops • Pollination service is sensitive to landscape change—loss of natural habitat. However . . . • Sensitivity depends on landscape structure. Pattern of habitat loss. • Proximity to patches of semi-natural habitat. Management Implications: • Retaining remnants of semi-natural habitat appear to be key. • Restoration of patches of natural habitat could help to bolster pollination. • Efforts to restore natural habitat should be focused in areas of greatest habitat loss.

  25. Augmenting floral resources in agricultural landscapes New Project: Hedgerows and Flowering forb strips for bees. • What plant species should be used ? . . . to benefit wild and managed bees • How much area set aside is beneficial?

  26. Hedgerow/ forb-strip restoration

  27. Developing Restoration Planting Recommendations Important plants for honey bees Important plants for native bees Williams, Mandelik, et al, In preparation

  28. 4 5 6 8 7 2 3

  29. Pollinators and pollination at the landscape scale • Restoration and conservation are expensive and sometime contentious. • How much land “should we” set aside or restore? • Can we consider different scenarios, before proposing implementation? • Can such scenarios be rooted in data? • Modeling pollinator communities across a landscape.

  30. Field and habitat types alfalfa beans tomato sunflower melon, squash maize, wheat walnut grapes prune pasture Oak woodland Chaparral Grassland Riparian Bare Field crops, rice

  31. Modeling habitat suitability and pollination service • Central place foragers • Different floral hosts • Diverse nesting biology 1000 m 500 m Habitats differ in quality for bees Different bee species access different habitats Same habitat type differs in value (suitability) for different bee species

  32. Map 1. NESTING SUITABILITY: Four guilds HNxz Stem Cavity Wood Ground

  33. HFxz Map 2. FLORAL AVAILABILTY, 500 m FORAGING RANGE Spring Summer 1 0.5 100 100 0.8 0.4 200 200 300 300 0.6 0.3 400 400 0.4 0.2 500 500 600 600 0.2 0.1 700 700 0 0 200 400 600 800 200 400 600 800 Fall 0.25 100 0.2 200 300 0.15 400 0.1 500 600 0.05 700 0 200 400 600 800

  34. Map 3. Composite pollinator source map

  35. Modeling habitat suitability and pollination service Use pollinator source map with foraging distance to predict the availability of pollinators on a given farm field

  36. More information • UC Davis Bee Biology http://beebiology.ucdavis.edu/ • Neal Williams Lab http://polleneaters.wordpress.com/

  37. Observed1 (y-axis) vs. Predicted (x-axis) Richness Abundance Availability (predicted) Availability (predicted)

  38. Assessing pollination by native bees • Amount of pollen deposited per visit by each bee species • Number of visits to a flowerby each bee species Pi Vi Total contribution =

  39. Ways of viewing pollination services Managed bees Wild bees Honey bees: Can honey bees fully pollinate? yes yes yes NO Honey bees Native bees other bees: Can other bees help pollinate? yes Managed bees Wild bees

  40. Increasing global demand for pollinator-dependent crops Aizen and Harder, 2009