The effect of simulated climate change on overwintering physiology in solitary bees and the impacts of floral and landscape resources on nesting Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Megan Frances Varvaro, B.S. Graduate Program in Evolution, Ecology, and Organismal Biology The Ohio State University 2018 Thesis Committee Karen Goodell, Advisor Agustí Muñoz-Garcia David Denlinger Rebecca Swab Copyrighted by Megan Frances Varvaro 2018 Abstract Solitary bees are crucial pollinators of agricultural and wild plants, and recent declines of these bees may be linked to habitat loss, parasites, pesticides, and climate change. Solitary bees are unique from solitary bees because each female builds her own nest out of collected materials, and these females only travel a few hundred meters from their nest on an average foraging or provisioning bout. This narrow foraging range implies that the proximity and quality of surrounding floral and landscape features affect nest production of solitary bees. After the nest is built, the immature bees must survive the winter to emerge the next summer as adults. In the fall, they enter diapause, a state of reduced metabolism, and then in the late winter, they enter post- diapause quiescence where metabolism is affected by external factors. As winter temperatures increase, they may expend more energy in these stages and burn more fat stores, resulting in less energy upon emergence, reduced fitness, or higher mortality. We wanted to investigate how the surrounding landscape impacts solitary bee nest production and how winter temperature increases associated with climate change may impact overwintering physiology. To test the first idea, we tracked Megachile rotundata nesting in artificial domiciles and surveyed the surrounding floral resources and landscape composition. We found that as the density of Lotus corniculatus in June increased, the number of nests established at a site also increased, and that as the distance from the nest to the forest increased, total number of brood cells per site decreased. Therefore, L. corniculatus density early in the season and proximity of i forested habitat, a potential source for leaves used as nesting material, impact M. rotundata nest production. This information is useful for managing natural populations of this bee, which is an abundant, non-native species in North America. To test how simulated climate change may impact solitary bee overwintering physiology, we examined how Megachile rotundata, Megachile campanulae, and Osmia cornifrons respond by measuring metabolic rate across diapause and post-diapause, modelling metabolic rate based on ambient and elevated temperature data, and by rearing individuals under ambient and elevated temperature to assess emergence, weight loss, and mortality. We found that with elevated diapause and post-diapause temperatures M. rotundata and M. campanulae metabolic rates are significantly higher. We also showed that M. campanulae had a higher rate of metabolism than M. rotundata. However, for modelled metabolic expenditure the elevated temperature treatment had lower total metabolic expenditure than the control treatment because the bees emerged earlier in the elevated temperature treatment. Bees in the elevated temperature treatment still showed high mortality, indicating that the elevated temperature treatment negatively affects them. Bees like M. campanulae, that had higher metabolic rates, and O. cornifrons, which had high mortality in the elevated temperature treatment, may be impacted more by temperature increases caused by climate change than other species. ii Acknowledgments I would like to thank my advisor Dr. Karen Goodell for all the support and guidance through my research and writing. I’ve learned and grown as a scientist because of her assistance, and I appreciate the encouragement she gave me throughout this challenging process. I would also like to thank Dr. Agustí Muñoz-Garcia for the teaching and guidance as well. His support added greatly to expanding my research project and scientific skill set. I would also like to thank Dr. David Denlinger and Dr. Rebecca Swab for taking an interest in my project and helping develop it fully. Additionally, I would like to thank my very supportive lab peers Dr. Jessie Lanterman, Andrew Lybbert, and James Hung for their encouragement and advice. To my friends, Danie Frevola, Tiara Stark, and Clara Bruner, thank you for encouraging me throughout this process. Finally, I would like to thank my mother, Kelly Murphy, for continued support and encouragement. iii Vita 2016........................……………………..............B.S. Nicholls State University 2016…………….......…………………………...Graduate Teaching Associate, College of Life Science Education, The Ohio State University 2017-18…………………………………………....Graduate Teaching Associate, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University Fields of Study Major Field: Evolution, Ecology, and Organismal Biology iv Table of Contents Abstract ................................................................................................................................ i Acknowledgments .............................................................................................................. iii Vita .................................................................................................................................... iiv List of Tables ..................................................................................................................... vi List of Figures ................................................................................................................... vii Chapter 1. The effect of simulated climate change on overwintering physiology in solitary bees ............................................................................................................................................. 1 Abstract ........................................................................................................................... 1 Introduction ..................................................................................................................... 3 Methods........................................................................................................................... 6 Results ........................................................................................................................... 13 Discussion ..................................................................................................................... 21 Chapter 2. The impacts of floral and landscape resources on nesting .............................. 26 Abstract ......................................................................................................................... 26 Introduction ................................................................................................................... 27 Methods......................................................................................................................... 29 Results ........................................................................................................................... 32 Discussion ..................................................................................................................... 35 Literature Cited ................................................................................................................. 39 Appendix A: All mixed model analysis tables for M. rotundata nesting. ........................ 42 v List of Tables Table 1.1: Equations predicting metabolic expenditure of two species of Megachile from temperature generated from best fit lines of the metabolic rate curves. Equations shown for the diapause period (Nov-Dec) and the post-diapause period (Feb-April). ............................ 11 Table 1.2: Analysis of covariance of log MR and log mass specific MR with temperature as a covariate, species, and temperature by species effects tested in diapausing and post-diapausing M. rotundata and M. campanulae ........................................................................................................................................... 16 Table 1.3: Generalized linear model analysis of modelled mass specific metabolic expenditure of M. rotundata and M. campanulae during diapause and post-diapause ........................................................................................................................................... 17 Table 1.4: Mixed model analysis for emergence day of M. rotundata, M. campanulae, and O. cornifrons ........................................................................................................................................... 19 Table 1.5: Mixed model analysis for weight loss of M. rotundata and M. campanulae .. 20 Table 2.1: Mixed model analysis of variance models chosen of M. rotundata nest production on floral resources and landscape composition ........................................................................................................................................... 35 Table A.1: Mixed model analysis of variance of the number of nests established and average L. corniculatus desity across the season ........................................................................................................................................... 42 Table A.2: Mixed