FACTORS INFLUENCING BEE COMMUNITIES AND POLLINATION SERVICES ACROSS AN URBAN ENVIRONMENT Justin D. Burdine A Dissertation Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 2019 Committee: Kevin McCluney, Advisor Mary-Jon Ludy Graduate Faculty Representative Andrew Gregory Helen Michaels Shannon Pelini ii ABSTRACT Kevin McCluney, Advisor Current declines in the abundance and diversity of bees and other pollinators has created uncertainty in their ability to reliably deliver pollination services. Recent studies examining urban bee communities show that bees respond to urbanization-mediated changes in land-use and environmental conditions. This includes increases in thermal and desiccation threats via urban heat island (UHI) effects that have not been well explored in bees. But it is unclear whether or how urbanization-related changes to pollinators influence pollination services. In this dissertation, I surveyed urban gardens and city parks across the metropolitan region of Toledo, Ohio (USA). First, I examined thermal and desiccation tolerances and safety margins for three bee species: silky striped sweat bees (Agapostemon sericeus), western honey bees (Apis mellifera), and common eastern bumble bees (Bombus impatiens). Second, I examined how urbanization and local habitat characteristics (herbaceous cover, floral abundance and color, tree abundance, canopy cover, soil moisture, gardens size) influenced bee communities (abundance, diversity, composition) and pollination services (visitation frequency). Third, I examined how bee species with specific functional traits and combinations of traits (functional guilds) were influenced by urbanization. The findings from this dissertation suggest that bees have differential sensitivities to urbanization, and managing for diverse bee communities in urban environments may require mitigating changes in temperature and water and increasing floral resource availability. iii To my wife. iv ACKNOWLEDGMENTS The first people I want to thank are the members of committee: Kevin McCluney, Shannon Pelini, Helen Michaels, Andrew Gregory, and Mary-Jon Ludy. They had a significant impact on my research design and methodology, and they shaped me into the scientist that I am today. My committee members also demonstrated how to find success in academia, and provided me with invaluable advice on work-life balance. My advisor, Kevin McCluney, was a great mentor and motivator that influenced my approach to teaching, research, and mentoring. Many individuals in the McCluney Lab made significant contributions to this dissertation: Jamie Becker, Margaret Duffy, Edward Lagucki, Melanie Marshall, Gabriella Metzner, Kaleigh Obrock, Rachel Paul, Melissa Seidel, Erin Plummer, and John Woloschuk. Many of you assisted me on important research projects, and spent hours sitting in front of a microscope looking at bees. Others listened to practice talks, proofread manuscripts and grant proposals, and helped me design conference posters. We shared meals and coffee breaks, and you all reassured me that I was not the only person who had no idea what they were doing. Thank you for doing life beside me as a graduate (or undergraduate) student. There were also many organizations and land owners that gave me permission to conduct research on their properties in Lucas and Wood County. I want to thank the Olander Park System, Wood County Parks System, The Nature Conservancy, and the Toledo Zoo. Multifaith Grows and Toledo Grows helped connect me with urban gardeners throughout the region, and I enjoyed getting to know each of the gardeners I worked with. I also want to thank all the gardeners for giving me your extra fruits, vegetables, and eggs. They were delicious. v Lastly, I want to think my wife and daughter for being supportive and loving. You both helped me enjoy each step in the dissertation process, and gave me a life outside of academia. So much life happened during these years and I am glad I had you two by my side. vi TABLE OF CONTENTS Page CHAPTER I: DIFFERENTIAL SENSITIVITY OF BEES TO URBANIZATION-DRIVEN CHANGES IN BODY TEMPERATURE AND WATER CONTENT ................................ 1 Introduction ................................................................................................................ 1 Methods...................................................................................................................... 5 Study Area ..................................................................................................... 5 Study Organisms ............................................................................................ 6 Field Body Temperature and Water Content ................................................. 6 Thermal and Water Content Limits Sampling ............................................... 7 Thermal Tolerance Experiment ..................................................................... 7 Desiccation Tolerance Experiment ................................................................ 8 Thermal and Hygric Safety Margins.............................................................. 9 Statistical Methods ......................................................................................... 9 Results ........................................................................................................................ 10 Critical Thermal Maximum (CTmax) .............................................................. 10 Critical Water Content (CWC) ...................................................................... 10 Thermal Safety Margin .................................................................................. 11 Hygric Safety Margin .................................................................................... 12 Discussion .................................................................................................................. 12 Thermal Tolerance ......................................................................................... 13 Desiccation Tolerance .................................................................................... 15 Thermal and Hygric Safety Margins.............................................................. 15 vii CHAPTER II: INTERACTIVE EFFECTS OF URBANIZATION AND LOCAL HABITAT CHARACTERISTICS INFLUENCE BEE COMMUNITIES AND FLOWER VISITATION RATES ........................................................................................................... 19 Introduction ................................................................................................................ 19 Methods...................................................................................................................... 22 Sampling Locations ....................................................................................... 22 Sampling Methods ......................................................................................... 22 Local Habitat Characteristics ......................................................................... 23 Visitation Rates .............................................................................................. 23 Statistical Methods ......................................................................................... 24 Results ........................................................................................................................ 25 Summary Statistics......................................................................................... 25 Community Composition ............................................................................... 25 Overall Abundance and Diversity .................................................................. 26 Visitation Rates .............................................................................................. 26 Discussion .................................................................................................................. 26 Impervious Surface ........................................................................................ 27 Canopy Cover ................................................................................................ 28 Flower Abundance ......................................................................................... 28 Caveats ........................................................................................................... 29 Conclusions .................................................................................................... 29 CHAPTER III: BEE GUILDS SHOW DISSIMILAR RESPONSES TO URBANIZATION IN A MEDIUM-SIZED CITY, ALTERING POLLINATOR VISITATION ................................ 31 viii Introduction ................................................................................................................ 31 Methods...................................................................................................................... 33 Sampling Locations ....................................................................................... 33 Sampling Methods ......................................................................................... 33 Habitat Characteristics ................................................................................... 34 Visitation Rates .............................................................................................. 35 Functional Traits ...........................................................................................