Global Change and Trophic Interaction Diversity: Complex Local and Regional Processes
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University of Nevada, Reno Global Change and trophic interaction diversity: complex local and regional processes A dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy in Ecology, Evolution, and Conservation Biology by Nicholas A. Pardikes Dr. Lee A. Dyer/Dissertation Advisor May 2017 THE GRADUATE SCHOOL We recommend that the dissertation prepared under our supervision by NICHOLAS PARDIKES Entitled Global Change And Trophic Interaction Diversity: Complex Local And Regional Processes be accepted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Lee Dyer, Ph.D, Advisor Matt Forister, Ph.D, Committee Member David Wagner, Ph.D, Committee Member Peter Weisberg, Ph.D, Committee Member Chris Jeffrey, Ph.D, Graduate School Representative David W. Zeh, Ph. D., Dean, Graduate School May, 2017 i ABSTRACT The structure and functioning of ecosystems across the globe are rapidly changing due to several components of global environmental change (GEC). My dissertation aims to illustrate how regional and local aspects of GEC impact diverse assemblages of species and species interactions. All organisms are embedded in complex networks of species interactions, and future efforts to predict and mitigate the impacts of GEC on ecological communities will be facilitated by such studies that incorporate a suite of species and species interactions. This study advances our understanding of how GEC will impact ecological communities by investigating two questions about GEC: 1) How will shifts in global climate cycles (e.g., El Nino Southern Oscillation), as a consequence of global warming, impact a diverse assemblage of butterflies that exist across a heterogeneous landscape? 2) What are the consequences of woody plant encroachment on complex, specialized interactions between plants, insect herbivores, and natural enemies (e.g., insect parasitoids)? Furthermore, I helped develop a tool to identify characteristics of ecological communities that are essential for promoting the diversity of trophic interactions. While the loss of species diversity is well recognized, interactions among species are vanishing at an astonishing rate, yet we know little about factors that determine the diversity of interactions within a community. Using data from a long-term butterfly monitoring dataset, I was able to demonstrate the utility of large-scale climate indices (e.g., ENSO) for modeling biotic/abiotic relationships for migratory butterfly species. Next, I used encroaching juniper woodlands in the Intermountain West to uncover that population age structure of dominant tress, such as juniper, can affect plant- insect dynamics and have implications for future control efforts in the expanding ii woodlands. Additionally, reductions of understory plant diversity, as a consequence of juniper expansion, resulted in significantly lower parasitism rates and parasitoid species diversity. Finally, simulated food webs revealed that species diversity and, to a lesser degree, consumer diet breadth, promote the diversity of trophic interactions. As ecosystems across the globe experience changes and the loss of species diversity continues, these findings offer insight into how GEC will impact species and species interactions. iii DEDICATION This dissertation is dedicated to my partner, Moria. Without your support and love, this work wouldn’t have been possible. Thank you for always being there when I needed it most. To the many adventures we have waiting for us and to all the great memories that made us who we are today. “May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view.” Edward Abbey iv ACKNOWLEDGMENTS I wish to thank my family for all of the support throughout this process. It is because of you that I developed my interest and love of science and nature. I also want to thank the Earthwatch Institute for providing me with an opportunity to work with a diverse group of citizen scientists. Teachers, students, and bankers all helped collect data used in this dissertation and it would not have been possible without their help. I also want to thank my advisor, Lee Dyer, for providing me with the opportunity to contribute to research in your lab. You have been instrumental in shaping me into the scientist I am today and introducing me to the magnificent world of plants and insects. Finally, I want to thank my partner, Moria, and our wonderful dog, Peanut, for bringing joy and happiness to my life. Life is so much fun with you two around. v TABLE OF CONTENTS ABSTRACT ......................................................................................................................... i DEDICATION ................................................................................................................... iii ACKNOWLEDGMENTS ................................................................................................. iv TABLE OF CONTENTS .....................................................................................................v LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ........................................................................................................... ix INTRODUCTION ...............................................................................................................1 CHAPTER 1 – Global weather and local butterflies: variable responses to a large-scale climate pattern along an elevational gradient ......................................................................6 Abstract ..............................................................................................................7 Introduction ........................................................................................................8 Methods............................................................................................................10 Results ..............................................................................................................14 Discussion ........................................................................................................19 Acknowledgments ............................................................................................25 Tables ...............................................................................................................26 Figure Legends .................................................................................................28 Figures..............................................................................................................30 Supplementary material ...................................................................................34 Appendix A………………………………………………………………35 Appendix B………………………………………………………………51 CHAPTER 2 - Preferences and performance of Juniper caterpillar assemblages in expanding juniper woodlands of the Intermountain West .................................................57 Abstract ............................................................................................................58 Introduction ......................................................................................................60 Methods............................................................................................................63 Results ..............................................................................................................70 vi Discussion ........................................................................................................75 Acknowledgments ............................................................................................82 Tables ...............................................................................................................83 Figure Legends .................................................................................................90 Figures..............................................................................................................94 Supplementary material .................................................................................101 CHAPTER 3 - Testing the enemies hypotheses in expanding juniper woodlands107 Abstract ..........................................................................................................108 Introduction ....................................................................................................110 Methods..........................................................................................................114 Results ............................................................................................................123 Discussion ......................................................................................................125 Acknowledgments ..........................................................................................132 Tables .............................................................................................................133 Figure Legends ...............................................................................................135 Figures............................................................................................................136 Supplementary material .................................................................................138 CHAPTER 4 - Trophic interaction diversity: simulated networks generate