THE EFFECT OF ANTHROPOGENIC HABITAT MODIFICATION ON INSECT- MEDIATED ECOSYSTEM SERVICES Audrey Maran 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 August 2020 Committee: Shannon Pelini, Advisor Nathan Hensley Graduate Faculty Representative Kevin McCluney Karen Root Michael Weintraub © 2020 Audrey Maran All Rights Reserved iii ABSTRACT Shannon Pelini, Advisor Human activity and land use negatively affect many arthropods that provide important ecosystem services. Agricultural land and cities are both common types of human-modified habitat that often have decreased arthropod richness and diversity, due in part to loss of habitat quantity, habitat complexity (i.e. habitat types available), and structural complexity (i.e. habitat density, shape, or height). This dissertation focuses on gaps in understanding of t he relationship between habitat complexity and arthropod-mediated ecosystem services in human-modified environments. In agricultural fields, we examined the response of ground arthropods, microbial activity, and nutrient pools to applications of a nutrient source (labile detritus: mayfly carcasses) and/or habitat structure (recalcitrant detritus: corn stover) over a 7-week period. In urban prairies, we examined the relationship between arthropod predators and complexity, and the impact that urban features have on that relationship at multiple scales. Throughout the work presented in this dissertation, we found that known patterns and relationships were disrupted or dampened in human-modified habitats. Though labile detritus recruited ground arthropods to agricultural fields, they did not stimulate nutrient cycling as they do in less-modified systems. The labile detritus provided nutrients but had little impact on microbial activity. These findings suggest that low baseline bi otic activity in agricultural fields lessens our ability to promote biotic nutrient cycling. In urban prairies, we found that on a small-scale, predator-prey ratio increased with structural complexity, but only structural complexity at lower heights and when the structural complexity was primarily due to forbs. Ons a larger cale, arthropod abundance and iv predation were best predicted by complexity within prairies, while arthropod community structure was best predicted by habitat complexity and urban features surrounding a prairie. Taken together, these findings suggest that in urban prairies, the surrounding complexity may determine which arthropods can find and/or persist in a prairie, while complexity within the prairie determines how many of the arthropods can be supported and perhaps even the ecosystem services they provide, once in the prairie. Ultimately, this dissertation fills gaps in the literature regarding the impact of habitat and structural complexity on arthropod ecosystem services in human-modified environments. v I dedicate this dissertation to my grandmother Jeanne Fair, whose interest in science could not be smothered by the societal expectations that limited her career options. vi ACKNOWLEDGMENTS The support system that I have been lucky enough to develop, comprised of family, friends, peers, mentors, and furry four-legged companions, never fails to amaze me. Though many of you have been there as long as I can remember, I specifically want to thank everyone for their support while I pursued my doctoral degree. I have leaned on you throughout this process, but particularly in the last two years, first as I moved states away, and now as I have worked to finish my dissertation while a pandemic has changed life as we all know it and our society is rightfully rising up against years of systemic racism and oppression. My parents, Norman and Wendy Maran have not just cheered for me from the sidelines, but helped build experiment equipment and even come into the field. My friends, old and new, have always been there to keep me sane and never complained when I had to cancel plans to get work done or was especially grumpy from exhaustion. Melissa Fleig and Jordan Passmore even helped me with tedious field equipment arts and crafts. I cannot begin to put into words how much my partner, Paul Best has helped me throughout the process, from encouragement and support to helping in the lab and field. He even got covered head-to-toe in mayflies for me, something I’m sure not many people could say of their spouses. At Bowling Green, so many wonderful people have contributed towards this dissertation, by sharing th eir wisdom, ideas, commiserating, and more. The biology department at BG is a truly special place, with faculty who have changed my life (thank you Jeff Miner, for encouraging me to become a scientist) and let me laugh, think, and even cry in their offices. Thank you to my committee, your guidance made this work possible; though you helped in countless ways, in particular I thank Kevin McCluney for helping me with invertebrate dynamics and statistics, Karen Root for helping me think on different scales and about vii community dynamics, Michael Weintruab for helping me think about soil, microbes, and soil biogeochemistry, and Nathan Hensley for providing big picture guidance. Thank you to Mary- Jon Ludy for stepping in for Nathan when I made a scheduling error. Shannon Pelini, my wonderful, badass advisor is unparalleled. I mean, who else’s description could elicit a “wow, she sounds great!” from anyone I tell about them? Shannon has been there for my entire graduate school experience. I have grown with her and gone through a number of life events with her, she helped me finally confront a long-standing battle with anxiety, she taught me how to be both a scientist and a mentor, and she taught me so many of the all-important “soft-skills” that helped me get where I am today. I could go on for ages about her, but instead I will say that if you haven’t been lucky enough to meet her, that you should, because she is a phenomenal person and you won’t leave an interaction with her without learning something about yourself or the world. Unsurprisingly, Shannon also recruits the most wonderful people to her lab (including her former lab manager and husband, Michael Pelini!). Rob Baroudi, Cari Ritzenthaler, Caitlin Maloney, Eric Moore, Amanda Winters, Josie Lindsey-Robbins, Preston Thompson, I could not have asked for better labmates and peers. Jessica Susser, honorary labmate, chapter 1 would literally not have happened without you. I also want to extend a special thank you to the undergraduate researchers who worked with me throughout my doctoral work, offering their help and growing into scientists alongside me: Jessica Swedick, Kristina Flanigan, Rachel Goldman, Jamie Hawkins, Sydnee Fenn, Andrew Sotherland, Eric Huber, and Catherine Freed. I could fill a book with the names of everyone who has helped me—thank you all. viii TABLE OF CONTENTS Page INTRODUCTION .................................................................................................................... 1 CHAPTER 1. DOES STIMULATING GROUND ARTHROPODS ENHANCE NUTRIENT CYCLING IN CONVENTIONALLY MANAGED CORN FIELDS? .................................... 8 Introduction ................................................................................................................... 8 Methods......................................................................................................................... 12 Study sites ......................................................................................................... 12 Experimental design.......................................................................................... 12 Arthropod sampling .......................................................................................... 14 Nutrient and microbial analyses ........................................................................ 14 Soil respiration .................................................................................................. 15 Soil nutrients and microbial biomass C, N, and P ............................................ 15 Soil enzymes ..................................................................................................... 16 Data analysis ..................................................................................................... 17 Results ........................................................................................................................... 19 Arthropods ........................................................................................................ 19 Soil microbial activity and nutrient dynamics .................................................. 19 Linking arthropods and microbial activity ........................................................ 20 Discussion ..................................................................................................................... 22 Conclusion .................................................................................................................... 26 Figures........................................................................................................................... 27 ix CHAPTER 2. DOES HABITAT STRUCTURAL COMPLEXITY PREDICT ARTHROPOD PREDATOR-PREY RATIO IN URBAN PRAIRIES? ............................................................ 35 Introduction ................................................................................................................... 35 Methods........................................................................................................................