Date of Award

Spring 2018

Project Type

Thesis

Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Sandra M Rehan

Second Advisor

Carrie Hall

Third Advisor

Janet Sullivan

Abstract

Though recent literature highlights widespread bee declines, detailed information on local communities, plant-pollinator network interactions and individual species remains distressingly scarce. In order to accurately direct conservation initiatives and to evaluate the status of wild bees and their host plants, long-term data on these populations is critical. Examining pollinator communities across regional scales highlights small-scale changes that go undetected in larger investigations. In light of unknown effects of introduced species and cumulative range expansions of exotic taxa, monitoring wild communities closely and extensively over time is becoming increasingly important. The focus of this thesis is to investigate a regional wild bee plant-pollinator network to identify changes and correlates of change over 125 years (1891-2016) in the species that comprise the wild bee and plant communities of New Hampshire.

Shifts in regional wild bee community composition impact ecological relationships corresponding with the species that become more or less represented as a result of these shifts. This study analyzed 119 wild bee species in New Hampshire to reveal that 16 species are proportionally declining and 18 species are proportionally increasing. Over half of the species found in decline experienced a significant elevational or latitudinal range shift, many are regionally important crop pollinators, and all are native New Hampshire taxa. Neither genus nor guild affiliations were found to be indicators of change, suggesting that the requirements and behavior of individual species must be examined in order to evaluate the current and future state of the wild bee community.

The mutualistic interactions of plant-pollinator networks provide myriad economic, ecological, and cultural functions without which there would be severe environmental and societal consequences. Because of globally intensifying anthropogenic land use and climate change, plant-pollinator networks are becoming increasingly vulnerable to disturbance. The wild bee community interacts with a diverse array of flowering plants with specific environmental needs. Examining interactions between wild bees and floral hosts offers powerful insight into pollinator ecology and has potential to detect temporal network variation within the community.

This study revealed that changes in the wild bee plant-pollinator network over the past 125 years are characterized by a striking increase in exotic bee and plant taxa, which could have a destabilizing effect on mutualistic interactions in combination with increasing temperatures and habitat loss. Notable specialist interactions between native taxa that were recorded in historical networks have been lost, most likely due to host plant shifts and competition from recent species introductions. Subsequent monitoring and conservation efforts focused on habitat restoration for declining wild bee and plant taxa are fundamental to the future preservation of native biodiversity.

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