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theses

Biodiversity in the landscape offers myriad benefits that are collectively known as ecosystem services. Provision of ecosystem services that benefit agriculture, such as pollination, is affected by landscape complexity surrounding farms. In this study, I examine three questions about pollination in a focal crop, highbush blueberry (Vaccinium corymbosum): 1) Is crop production limited by pollination from honey and native bees? 2) At what scale does land cover control pollination services provided by native bees? 3) Are rare and declining native bees found in agricultural habitats? I found two lines of evidence for pollen limitation: first, berries receiving supplemental hand-pollination were generally heavier than berries receiving ambient pollination; second, mean berry mass increased significantly and non-asymptotically with honey bee flower visitation rate. I also found that native bees contribute an average of 14% (range: 0 -58%) of pollination to blueberry crops. Overall, I found that pollination may be a limiting factor in commercial fruit production. Additionally, I found that native bees responded more strongly to farm-scale than to landscape-scale land cover, but the scale at which land cover had the strongest effect varied by bee body size. Large bees showed a negative response to increasing agricultural cover at both scales, but were most strongly affected by the landscape scale. Small bees were negatively affected by agricultural land cover but only at the farm scale, while they had a small positive response to agricultural cover at the landscape scale. Aggregate pollination services from native bees were more strongly influenced by local agricultural cover, due to the combined effects of both large and small bees responding at that scale. These results suggest that local-scale management changes could have significant impacts on native bee abundance in agricultural fields. Finally, I found that rare bees were surprisingly abundant in agricultural habitat, with larger than expected abundances of a few species. These results were largely, but not entirely, driven by the abundance of crop specialist bees in crop fields. I also found high complementarity between agricultural habitat sub-types but not between natural habitat sub-types, suggesting that diverse crops may bolster bee species richness in agricultural areas.

ETD_6305

Ph.D.

Includes bibliographical references

by Faye Benjamin

doi:10.7282/T3T155G4

ETD doctoral

The author owns the copyright to this work.