Date of Award:

2016

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Ecology

Advisor/Chair:

Edward W. Evans

Abstract

Wild, native bees (Hymenoptera: Apoidea) provide pollination services valued at nearly $3 billion to U.S. agriculture annually, and are the primary pollinators maintaining plant communities in natural landscapes, an ecosystem service of incalculable worth. Global concern over widespread honeybee declines has spurred research to save that single species, while knowledge of the health and habitat requirements of 20,000 native bee species worldwide lags behind. Understanding dynamics and habitat associations of pristine native bee communities may help inform conservation priorities and restoration goals to ensure the widespread longevity of native bees. We surveyed the bee and plant communities over two flowering seasons and across four distinct habitat types (Alluvial, Live Oak Woodland, Blue Oak Woodland, and Grassland) at Pinnacles National Park, a protected biodiversity hotspot, and a pristine, heterogeneous environment. We collected 52,853 bee specimens over 308 collector days, and increased the species inventory to 479, from the previous 398 recorded as of the late 1990s. This statistic ranks Pinnacles as likely the most densely diverse area for native bees currently known.

Spatially, no relationship between habitat type and bee abundance or richness was observed. Bee species composition in Alluvial habitats, however, was more unique and showed lower dispersal, suggesting this habitat may serve as a nesting refugia for a core community of resident species. Temporally, we evaluated potential resilience of solitary bees to anticipated disruptions in bloom availability via novel, community-wide foraging on honeydew sugars produced by scale insects. We observed 56 native bee species using honeydew sugars during the early season low bloom, and determined that they locate this resource without visual cues. Overall, these findings suggest that native bee communities at Pinnacles National Park may be buffered against temporal resource shifts and may benefit from protection of the Alluvial habitat type. The patterns observed here should be evaluated in other locations to determine their value towards forecasting and managing widespread risks to native bees.

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