Land uses that support wild bee (Hymenoptera: Apoidea: Anthophila) communities within an agricultural matrix A DISSERTATION SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Elaine Celeste Evans IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Dr. Marla Spivak December 2016 © Elaine Evans 2016 Acknowledgements Many people helped me successfully complete this project. Many years ago, my advisor, mentor, hero, and friend, Marla Spivak, saw potential in me and helped me to become an effective scientist and educator working to create a more bee-friendly world. I have benefitted immensely from her guidance and support. The Bee Lab team, both those that helped me directly in the field, and those that advised along the way through analysis and writing, have provided a dreamy workplace: Joel Gardner, Matt Smart, Renata Borba, Katie Lee, Gary Reuter, Becky Masterman, Judy Wu, Ian Lane, Morgan Carr- Markell. My committee helped guide me along the way and steer me in the right direction: Dan Cariveau (gold star for much advice on analysis), Diane Larson, Ralph Holzenthal, and Karen Oberauser. Cooperation with Chip Eullis and Jordan Neau at the USGS enabled detailed land use analysis. The bee taxonomists who helped me with bee identification were essential for the success of this project: Jason Gibbs, John Ascher, Sam Droege, Mike Arduser, and Karen Wright. My friends and family eased my burden with their enthusiasm for me to follow my passion and their understanding of my monomania. My husband Paul Metzger and my son August supported me in uncountable ways. My parents, Bob and Liz Evans, are probably more excited than anyone about my accomplishments. My mother-in-law Dr. Marcia Walsch showed the way to achieve academic excellence, maintain broad interests in the world, all while raising a family. My friends Amy Krueger, Marlijn Hoogendoorn, and Lesley Tylczak all make the world a better place all the time. Much love to my dogs Scooter and King. My musical community helped provide essential life balance: International Novelty Gamelan, Milo Fine, Emel Sherzad, Jim Harpole, and Daniel Furuta. i Dedication This thesis is dedicated to Bombus terricola , once the most common bees in eastern North Dakota, now <0.00001% of the bees there. It is my hope that habitat improvements such as those recommended in this work can help populations of this and other bees suffering declines recover and remain a part of our world. ii Abstract My main aim in this thesis was to explore if there are habitat elements within the agricultural matrix that support bee diversity and abundance. I examined the influence of land-use on bee diversity in a predominantly agricultural landscape at sites varying in habitat thought to be bee-friendly, such as semi-natural lands, grasslands, and crops providing bee forage. I sought to determine whether and to what extent these potentially bee-friendly land uses support diverse bee communities. Bees found near crops not providing forage, including corn, soybean, and wheat, had less functional diversity. Bees found near semi-natural lands that contained flowers providing bee forage had increased functional diversity. Wooded areas were associated with increased bee species richness and bee abundance, and wetlands were associated with greater bee abundance. Crops providing bee forage were associated with increased bee species richness and diversity. Altering land management practices to promote retention and enhancement of these land uses will help support diverse wild bee communities within agricultural matrices. I also compared responses of wild bees and commercially managed honey bee colonies to bee-friendly land uses. Both honey bees and wild bees responded positively to semi-natural lands and crops providing bee forage. Examination of past and present bee and floral visitation records revealed a 16 to 30% loss of species richness. The bee genera Lasioglossum , Mellisodes, Halictus, and Ceratina increased in relative abundance more than 50%, while the genera Bombus, Megachile, and Colletes, decreased in relative abundance more than 65% and the genus Andrena decreased in relative abundance by 47%. The plant genera that received the most bee visits from 2010 to 2012 were Melilotus, Sonchus, and Cirsium, while the plants with the highest number of bee species visitors were Solidago, Cirsium , and Sonchus . The plant genera Zizia , Hydrophyllum , and Dalea all received more visitation in the past. This survey of flower visitors revealed a community in need of conservation with a remaining species pool to enable recovery given improvements in available habitat. iii Table of Contents Acknowledgements .......................................................................................................... i Dedication ........................................................................................................................ ii Abstract ........................................................................................................................... iii List of Tables ................................................................................................................. vii List of Figures ................................................................................................................. ix Chapter 1 . ....................................................................................................................... 1 1.1 Importance of bees for pollination .................................................................... 1 1.2 Bee natural history ............................................................................................ 2 1.2.1 Bee Phylogeny .............................................................................................. 2 1.2.2 Bee habitat .................................................................................................... 2 1.2.3 Solitary and social bees ................................................................................. 4 1.2.4 Life history traits of Northern Great Plains bee genera ................................ 5 1.3 Bee decline ........................................................................................................ 8 1.3.1 Habitat Loss ................................................................................................ 10 1.3.1.2 Nesting resources .................................................................................... 11 1.3.2 Land use ...................................................................................................... 11 1.3.3 Pesticides..................................................................................................... 13 1.3.4 Climate Change ........................................................................................... 14 1.3.5 Introduced species ....................................................................................... 15 1.3.6 Competition among bees............................................................................. 15 1.3.7 Natural Enemies .......................................................................................... 16 1.3.8 Pathogens .................................................................................................... 17 1.4 Agricultural land uses supporting wild bee communities ............................... 17 1.5 Response of honey bees and wild bees to pollinator habitat .......................... 19 1.6 Bees and other flower visitors in agricultural lands in the prairie pothole region of North Dakota .......................................................................................................... 20 1.7 Future directions ............................................................................................. 22 iv Chapter 2 . ..................................................................................................................... 24 2.1 Introduction ........................................................................................................... 25 2.2 Methods........................................................................................................... 27 2.2.1 Study area.................................................................................................... 27 2.2.2 Survey locations .......................................................................................... 28 2.2.3 Landscape characterization ......................................................................... 28 2.2.4 Wild bee survey .......................................................................................... 30 2.2.5 Statistical analyses ...................................................................................... 36 2.3 Results ............................................................................................................. 37 2.3.1 Bee diversity ............................................................................................... 38 2.3.2 Bee community measures related to land use ............................................. 39 2.3.3 Floral use by bees........................................................................................ 40 2.4 Discussion ....................................................................................................... 41 2.5 Figures............................................................................................................. 47 2.6 Tables .............................................................................................................