University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 2021 TROPICAL PLANT-ANIMAL INTERACTIONS: LINKING DEFAUNATION WITH SEED PREDATION, AND RESOURCE- DEPENDENT CO-OCCURRENCE Peter Jeffrey Williams Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation Williams, Peter Jeffrey, "TROPICAL PLANT-ANIMAL INTERACTIONS: LINKING DEFAUNATION WITH SEED PREDATION, AND RESOURCE-DEPENDENT CO-OCCURRENCE" (2021). Graduate Student Theses, Dissertations, & Professional Papers. 11777. https://scholarworks.umt.edu/etd/11777 This Dissertation is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. TROPICAL PLANT-ANIMAL INTERACTIONS: LINKING DEFAUNATION WITH SEED PREDATION, AND RESOURCE-DEPENDENT CO-OCCURRENCE By PETER JEFFREY WILLIAMS B.S., University of Minnesota, Minneapolis, MN, 2014 Dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biology – Ecology and Evolution The University of Montana Missoula, MT May 2021 Approved by: Scott Whittenburg, Graduate School Dean Jedediah F. Brodie, Chair Division of Biological Sciences Wildlife Biology Program John L. Maron Division of Biological Sciences Joshua J. Millspaugh Wildlife Biology Program Kim R. McConkey School of Environmental and Geographical Sciences University of Nottingham Malaysia Williams, Peter, Ph.D., Spring 2021 Biology Tropical plant-animal interactions: linking defaunation with seed predation, and resource- dependent co-occurrence Chairperson: Jedediah F. Brodie Plant-consumer interactions can be critical for regulating populations of both plants and animals. In the tropics, many trees rely on animals to disperse their seeds, but many of these dispersers are disappearing, with potentially disastrous consequences for tropical tree species and global carbon storage. Defaunation—the loss of large animals due to factors such as overhunting—can also affect seed fates, either by increasing or decreasing seed predation. We know that defaunation alters these plant-animal interactions, but we still do not know how these changes at early life stages will ultimately affect tropical tree populations. Furthermore, we do not understand how defaunation will affect overall seed survival because we do not know the extent to which other seed enemies will compensate when large seed predators are removed. Besides the effects of animals on plants, plants provide food resources that influence the ecology of consumers. In tropical Southeast Asia, dipterocarp mast fruiting results in highly variable fruit and seed resources over time, and logging alters the abundance and distribution of resources in different areas. These changes in resources may affect the behavior and co-occurrence of consumers, but it is unclear how other species will respond given the presence of key mast consumers. To study this, we would want to measure species’ responses to each other at fine spatiotemporal scales, but co-occurrence studies usually consider spatial or temporal co-occurrence separately. In Chapter One of this dissertation, I review the literature on how defaunation affects tropical trees. Then I explore how defaunation may ultimately affect population dynamics by applying defaunation effects to matrix population models of tropical tree species. In Chapter Two, I use experimental treatments in a tropical forest in Borneo to test for functional redundancy among four key groups of seed predators—large mammals, small rodents, insects, and fungi—in terms of their impacts on seed mortality and germination. Finally, in Chapter Three, I develop a novel method of analyzing co-occurrence in space and time concurrently, which I use to assess how associations among frugivore-granivore vertebrate species differ according to resource conditions. For this analysis, I use camera trap and fruit abundance data from a tropical forest in Malaysian Borneo. ii ACKNOWLEDGMENTS As it turns out, getting a PhD is not so easy. The only reason I have been able to complete this dissertation is thanks to the support, help, and mentorship of countless people—too many people to list. But I will try my best to express my gratitude to many of them here. First, I want to thank my advisor Jedediah Brodie for giving me the opportunity to do research in his lab, for encouraging me when I felt lost, and for mentoring me to become a professional scientist. Thank you to my committee members: John Maron, Kim McConkey, and Josh Millspaugh, and Winsor Lowe. Your guidance, feedback, and support have been invaluable, and my research is much stronger as a result. I want to thank Angie Luis, whom I consider my unofficial sixth committee member. The Ecology and Evolution program here at UM has been an incredible place to spend five years. Thank you to all of the professors and administrative staff, and thank you to all of the postdocs and fellow grad students, many of whom are now dear friends. I also want to thank all of my labmates in the Brodie lab: Daniel Bird, Tanner Humphries, Diandra Lewis, Shu Woan Teoh, Jen Wall, Scott Waller, and Sara Williams. When I arrived in Missoula, there was no one else. Now I leave a thriving lab full of wonderful human beings. Thank you to former Brodie lab member Alys Granados, whose research strongly shaped the direction of my PhD. I want to thank the UM School of Music jazz program for giving me an outlet to do something other than research. My fieldwork in Sabah, Malaysian Borneo would have been impossible without the amazing people who helped me with my research. I want to thank my hardworking field assistants, now also my friends, Musa Markus, Anthony “Tambi” Karolus, James “Bob” Suffian, Natami Thomas, Sabri, and Zinin. Thank you to everyone at Danum Valley Field Center, especially Mike Bernadus, Alex Karolus, Frederica “Ica” Karolus, and Johnny Laurens. At Malua, thank you Remmy Murus and Mikey O’Brien. I also want to thank Robert Ong and Glen Reynolds. To all of you, terima kasih banyak! Harap harap saya boleh kerja di Sabah lagi. I want to thank my family, Mom, Dad, Amy, and Alex. To my parents, in addition to helping with fieldwork for one day, thank you for supporting my obsession with wildlife and ecology since an early age, and thank you for supporting me throughout my PhD. And lastly, thank you Emily Kopania. You are great. Actually, the best. TABLE OF CONTENTS Abstract ............................................................................................................................... ii Acknowledgements ............................................................................................................ iii Table of Contents ............................................................................................................... iv Chapter 1: Defaunation-induced changes in seed predation may affect tropical tree populations more strongly than reduced seed dispersal ................................................1 Abstract ..........................................................................................................................2 Introduction ....................................................................................................................3 Methods..........................................................................................................................5 Results ..........................................................................................................................11 Discussion ....................................................................................................................12 References ....................................................................................................................16 Tables and figures ........................................................................................................21 Supplementary material Supplemental methods ...........................................................................................26 Supplemental tables ...............................................................................................29 Supplemental figures .............................................................................................47 Supplemental references ........................................................................................50 Chapter 2: Fungi and insects compensate for lost vertebrate seed predation in an experimentally defaunated tropical forest .....................................................................56 Abstract ........................................................................................................................57 Introduction ..................................................................................................................57 Results ..........................................................................................................................61 Discussion ....................................................................................................................62 Methods........................................................................................................................67