A Quantitative Assessment of Arboreality in Tropical Amphibians Across an Elevation Gradient: Can Arboreal Animals Find Above-Ground Refuge from Climate Warming?
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by ScholarBank@NUS A quantitative assessment of arboreality in tropical amphibians across an elevation gradient: can arboreal animals find above-ground refuge from climate warming? Brett Ryan Scheffers M.Sc. (Ecology) University of Alberta, Alberta, Canada A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF BIOLOGICAL SCIENCES NATIONAL UNIVERSITY OF SINGAPORE 2014 1 DECLARATION I hereby declare that this thesis is my original work and it has been written by me in its entirety. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. Brett Ryan Scheffers 22 October 2013 2 Acknowledgements Many sacrifices were made to obtain this PhD. Many of the people in this Acknowledgment section know of these sacrifices and were likely on the receiving end. My mother and father instilled and stressed the importance of having a strong work ethic. Without their sound upbringing, love, and constant encouragement, my thesis would not have been as long in length…literally. The old colloquial saying “dogs are a man’s best friend” speaks true to my heart. Guinness and I became companions in 2004 and he has been my dog and friend through every stage of my higher academic development. I thank Grandma, Scott, Craig, Amy, Jill, Jack, Ella, Madilyn, Faythe, Willard, Uncle J, Jennifer, and Nicky for their love and support. Jennifer Ornstein loved and supported me during various stages of this thesis. We shared this thesis together as many of my headaches often fell upon her. She remained devoted to me and her commitment and support warrants more than a simple ‘thank you’. Navjot Sodhi taught me how to “play the game” and to look at academia with a smile. The two years we spent together were likely the two most important years of my academic development. Carlos is my oldest and dearest friend. He’s proofed my papers from the beginning of my undergraduate degree through the finalization of this thesis. Most importantly, Carlos has pushed me to retain my creativity and imagination as Science can at times dull the senses. Because of Carlos, the world to me remains mystical. Bert and I seem to be each other’s shadow. Bert supported every step of this PhD and without him it would have been a lesser experience. He encouraged me to study Asplenium ferns and to monitor hunting activity at my field site. Our trip to Trus Madi in Borneo was the groundbreaking trip for my ‘arboreality hypothesis’ outlined in Chapter 2. Luke provides my life with constant entertainment. He is my conference buddy, my drinking buddy and our “dates” made this thesis not only tolerable but very enjoyable. Steve, Yvette, Kyle and Zac provided me with family and a home away from home. Their love and support has been unwavering over the past two years. Theo Evans, Stephen Williams, Bill Laurance and Richard Corlett all provided superb guidance and support during my thesis. I thank Arvin Diesmos from the National Museum of the Philippines for his support. 3 I thank the local community of Mt. Banahaw for supporting my research and Rafe, Warren, P. A. Buenavente, A. Barnuevo, B. Brunner, S. Ramirez, R. Willis, and M. Wise for assistance in the field. I thank the NUS faculty for all their support. I especially thank David Bickford and Ted Webb. Rafe Brown, David Edwards, Larry Heaney, Ben Phillips, Leighton Reid, and Luke Shoo provided great discussion throughout the development of this thesis. Financial support was provided by the Singapore International Graduate Award, Wildlife Reserves Singapore Conservation Fund, Australian Government National Environment Research Program, and the Australian Research Council. I’m forgetting someone…thank you. 4 I dedicate my PhD to my grandpa Scheffers and my awesome dog Guinness. They taught me the importance of long walks in the woods. 5 TABLE OF CONTENTS ACKNOWLEDGEMENT 3 SUMMARY 11 LIST OF TABLES 16 LIST OF FIGURES 17 CHAPTER 1 General introduction 18 CHAPTER 2 Increasing arboreality with altitude: a novel 29 biogeographic dimension CHAPTER 3 Bird’s nest ferns amplify biodiversity: 62 as long as they stay wet. CHAPTER 4 Thermal buffering of microhabitats is a 88 critical factor mediating warming vulnerability of frogs in the Philippine biodiversity hotspot. CHAPTER 5 Microhabitats reduce animal’s exposure 108 to climate extremes CHAPTER 6 General discussion 127 BIBLIOGRAPHY 138 6 Table of Contents Declaration......................................................................................................................................1 Acknowledgement ...................................................................................................................................... 3 Summary.................................................................................................................................................... 11 List of tables .............................................................................................................................................. 16 List of figures ............................................................................................................................................ 17 Chapter 1: Thesis introduction ...................................................................................................18 1.1 Where they live .............................................................................................................................. 19 1.2 Are missing species different ....................................................................................................... 23 1.3 Prospects ......................................................................................................................................... 23 1.4 Unknown biological dimensions ................................................................................................. 24 Chapter 2: Increasing arboreality with altitude: a novel biogeographical dimension ..........29 2.1 Introduction .................................................................................................................................... 29 2.2 Materials and methods .................................................................................................................. 31 2.2.1 Study areas ................................................................................................................................... 31 2.2.2 Vertical stratification of frogs across an elevation gradient ................................................. 32 2.2.3 Surveys in Singapore .................................................................................................................. 33 2.2.4 Environmental temperatures ..................................................................................................... 34 2.2.5 Elevation gradient of species richness and arboreality in the Philippines .......................... 34 2.2.6 Data Analysis and Kernel-density estimation ......................................................................... 35 2.2.7 Dehydration and arboreality ...................................................................................................... 36 2.2.8 Alternative hypotheses ............................................................................................................... 37 2.2.9 Linear models .............................................................................................................................. 38 2.2.10 Diagram of height and elevation shifts .................................................................................. 39 2.3 Results ............................................................................................................................................. 39 2.4 Discussion ....................................................................................................................................... 53 2.4.1 Research Caveats and Future Prospects .................................................................................. 57 7 2.4.2 Arboreality Under Climate Change .......................................................................................... 58 Chapter 3: Bird’s nest ferns amplify biodiversity: as long as they stay wet ..........................62 3.1 Introduction .................................................................................................................................... 62 3.2 Methods ........................................................................................................................................... 64 3.2.1 Study area .................................................................................................................................... 64 3.2.2 Bird’s nest fern and paired sampling surveys ......................................................................... 65 3.2.3 Ground to canopy tree surveys—frog occurrence in rainforest canopies ........................... 66 3.2.4 Bird’s nest fern characteristics .................................................................................................. 67 3.2.5 Garden Experiments—link between temperature buffering and precipitation ................... 68 3.2.6 Analysis—predictors of abundance ......................................................................................... 69 3.2.7 Predictors of occurrence