ABSTRACT Title of Dissertation: DIVERSITY AND STRUCTURE OF METROSIDEROS POLYMORPHA CANOPY ARTHROPOD COMMUNITIES ACROSS SPACE AND TIME Elske Karolien Tielens, Doctor of Philosophy, 2019 Dissertation directed by: Dr. Daniel S. Gruner, Department of Entomology Global biodiversity is under pressure from climate change, habitat fragmentation and other anthropogenic change, and our ability to predict biodiversity responses to change requires a better understanding of the processes that drive diversity and structure local communities. However, quantifying these processes has proven to be challenging for multiple reasons; diversity is multidimensional, and both diversity and the processes that generate it vary across scale. In this dissertation, I examine temporal and spatial patterns in community structure to test hypotheses about the drivers of local diversity and composition in communities of varying age, focusing on arthropod communities associated with the native tree Metrosideros polymorpha on the Hawaiian Islands. Analysis of Hemiptera (true bug) communities reveals a temporal pattern in community structure, where young substrate communities were variable in species composition and beta dispersion decreased with substrate age, indicating convergence. However, substrate age did not correlate with community dissimilarity in a directional way. Similarly, geographic distance did not correlate with compositional dissimilarity, suggesting a lack of dispersal limitation. I confirmed this result by examining connections between arthropod communities in a historically fragmented ‘kīpuka’ landscape, using species-area relationships and graph theory analyses. Finally, if canopy arthropods are dispersive and differences in species composition across sites are not driven by substrate age, local habitat characteristics may influence species composition. I determined the role of local beta diversity and identified habitat characteristics regarding forest structure and host leaf traits that are strong drivers of beta diversity and species composition. Then, to further explore local habitat drivers I examined forests with high intraspecific variation in co-occurring Metrosideros. In this hybrid zone, insect life history traits shape species’ response to intraspecific variation in host plant characteristics, highlighting the importance of including dimensions of biodiversity beyond taxonomic diversity. Together, these results demonstrate the importance of local habitat conditions for canopy arthropods, suggest that canopy arthropod communities are highly connected and that substrate age plays a limited role in determining local arthropod communities. Such insights into biodiversity and plant-insect interactions across temporal and spatial scale are integral to understanding and conserving our natural world. DIVERSITY AND STRUCTURE OF METROSIDEROS POLYMORPHA CANOPY ARTHROPOD COMMUNITIES ACROSS SPACE AND TIME by Elske Karolien Tielens Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2019 Advisory Committee: Professor Dr. Daniel S. Gruner, Chair Dr. Maile C. Neel Dr. John D. Parker Dr. Jeff W. Shultz Dr. Nathan G. Swenson © Copyright by Elske Karolien Tielens 2019 Preface This dissertation contains an introduction (Chapter I), three research chapters (Chapters II-IV), and a conclusion (Chapter V). Chapter III was previously published in the open access journal Ecosphere. For this manuscript, my contribution included conceptual development of the chapter, data analysis, writing and manuscript preparation. I thank my co-authors for their contributions to setting up the study, data collection, data extraction and editing. Chapter III is reprinted here in full under Creative Commons Attribution License (CC-BY). Assistance in funding, editing and data collection for all other chapters is stated in the acknowledgements. Appendices to all chapters are provided at the end of the dissertation as well as a single bibliography for literature cited throughout. ii Dedication For ʻōhiʻa lehua; the strong, resourceful and beautiful tree that forms the foundation of so much Hawaiian life “One describes a tale best by telling the tale. You see? The way one describes a story, to oneself or to the world, is by telling the story. It is a balancing act and it is a dream. The more accurate the map, the more it resembles the territory. The most accurate map possible would be the territory, and thus would be perfectly accurate and perfectly useless. The tale is the map that is the territory. You must remember this.” - Neil Gaiman 2001 iii Acknowledgements This work could not have been completed without the hard work and support of many colleagues and friends. This list is far from complete. I would like to thank my advisor, Dan Gruner, for bringing me up into the ʻōhiʻa canopy in the first place, for inspiring me with his love of Hawaiian arthropods, and for his support over the past six years. I would like to thank my committee; John Parker, Jeff Schultz, Nate Swenson, and in particular Maile Neel for their guidance. Maile, our conversations were integral in energizing me and reminding me of the joy in doing science. This work was made possible through generous funding by The Explorers Club, the University of Maryland’s Department of Entomology and Biological Sciences Graduate School, and the National Science Foundation. The Institute for Pacific Island Forestry welcomed me and provided me with a home base, as well as logistical support, during my time on Hawai‘i. I especially want to thank Christian Giardina and Kainana Francisco. The National Park Service, the Nature Conservancy, Hawaii Department of Land and Natural Resources provided us with access to the forest, and many landowners including Parker Ranch and Ponoholo Ranch graciously allowed us to traverse their land to access our field sites. Many hands helped collect this data, including Tom, Ari, Brendan, Sam, Maddie, Leah, Lindsey, Loreto, Giovanni, Nicole, Marina, Victor, Max, Lily, Hashem, Betsy, Yaroslava, and others. I am indebted to Britt Cole, whose competence, familiarity with the forest, endurance, knowledge of cars, and skills to fix anything and everything made my fieldwork easy, and without whom I might not have come home safely each day. Curtis Ewing was a source of great knowledge on Hawai‘i and its arthropods as well as a key partner in the field. My work was also shaped by the Hawaii Dimensions of Biodiversity team and our endless skype calls. I would not have learned as much as I have without the input from the Evolab at UC Berkeley. Rosemary Gillespie and George Roderick have been generous with their time, thoughts and resources to help me sharpen my ideas around evolution on the Hawaiian Islands, and I am grateful to all the graduate and undergraduate Evolab members that helped with data collection and fieldwork. The Gruner lab has been a wonderful place to spend these past years, and I am grateful for the university community. Kristen made this dissertation possible with her skills in insect identification, with her many stories that kept me sane in lonely times, and her willingness to even share a 10 m2 living space with me. I want to thank Alex Forde for his snark and his critical scientific insight (in that order), Mayda for her thorough edits, Gussie for her unfailing faith in my work, and Cora for all things, from boxing to brainstorming. Nicola contributed a touch of Europe and great biking commutes. Alex Novarro blazed the trail for me and is still in all things my example. I am deeply grateful for the love and support of my friends and family, in the United States and at home. I will not mention everyone here, but you all brighten my life. I am not sure I would have finished this process if it weren’t for the faith community I found at St Stephen and the Incarnation in Washington D.C. Lastly, I am grateful to Casey for being my partner in adventures big and small. iv Table of Contents Preface ........................................................................................................................... ii Dedication .................................................................................................................... iii Acknowledgements ...................................................................................................... iv Table of Contents .......................................................................................................... v List of Tables ................................................................................................................ vi List of Figures ............................................................................................................. vii Chapter 1 : Introduction ................................................................................................ 1 Conceptual background ............................................................................................. 1 Approaches in this dissertation ................................................................................. 7 Study system ........................................................................................................... 13 Outline of this dissertation ...................................................................................... 20 Chapter 2 : Local habitat, not dispersal limitation or geological substrate age, drives insect b-diversity