LOCAL AND REGIONAL INFLUENCES ON ARTHROPOD COMMUNITY STRUCTURE AND SPECIES COMPOSITION ON METROSIDEROS POLYMORPHA IN THE HAWAIIAN ISLANDS A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI'I IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ZOOLOGY (ECOLOGY, EVOLUTION AND CONSERVATION BIOLOGy) AUGUST 2004 By Daniel S. Gruner Dissertation Committee: Andrew D. Taylor, Chairperson John J. Ewel David Foote Leonard H. Freed Robert A. Kinzie Daniel Blaine © Copyright 2004 by Daniel Stephen Gruner All Rights Reserved. 111 DEDICATION This dissertation is dedicated to all the Hawaiian arthropods who gave their lives for the advancement ofscience and conservation. IV ACKNOWLEDGEMENTS Fellowship support was provided through the Science to Achieve Results program of the U.S. Environmental Protection Agency, and training grants from the John D. and Catherine T. MacArthur Foundation and the National Science Foundation (DGE-9355055 & DUE-9979656) to the Ecology, Evolution and Conservation Biology (EECB) Program of the University of Hawai'i at Manoa. I was also supported by research assistantships through the U.S. Department of Agriculture (A.D. Taylor) and the Water Resources Research Center (RA. Kay). I am grateful for scholarships from the Watson T. Yoshimoto Foundation and the ARCS Foundation, and research grants from the EECB Program, Sigma Xi, the Hawai'i Audubon Society, the David and Lucille Packard Foundation (through the Secretariat for Conservation Biology), and the NSF Doctoral Dissertation Improvement Grant program (DEB-0073055). The Environmental Leadership Program provided important training, funds, and community, and I am fortunate to be involved with this network. For clerical support, I am thankful to Lori Yamamura, Irene Shigano, Sally Oshiro, Jennifer Sunada, Susan Luke, Susan Yokouchi, Shannon Oshiro, Diane Butler, and especially Audrey Shintani and Rena Duhl for transcending my ignorance of University policies on grant management. The Hawai'i Department ofLand and Natural Resources, Division ofForestry and Wildlife (especially Jon Giffin on the Big Island), Nature Conservancy, National Park Service, and Parker Ranch provided research permits and/or field access. Collaboration with Dan Polhemus, collecting canopy arthropods III 1996 and 1997, kickstarted this project. I am grateful to Scott Fretz, Bob Peck and the late Wayne v Gagne for their pioneering work on Metrosideros arthropod communities on Hawai'i Island. Kirsten Heckmann, Sierra McDaniel, Emahlie McDaniels and Lauren Wilson were exemplary, conscientious field and laboratory assistants. lowe special debts of gratitude to Kirsten for collaborating on the design and implemention of plots and bird exclusion cages on the unforgiving terrain of the 1881 lava flow, and to Emahlie who volunteered her time for four months. Susan Cordell, Patrick Hart, Stephen Hight, Nancy Everett, Bob Cabin, Gus Bodner, Lou Santiago, Scott Fretz, Heraldo Farrington, Ross Langston, Leilani Durand, Danielle Feinholz, and Petr Nilsson also lugged fertilizer or helped to build cages during field stints. Rebecca Forkner, Jon Price and Paul Krushelnycky deserve special mention for stimulating conversation, critical comments on manuscripts, and collaboration. David Foote was helpful with logistics on the Big Island, and provided crucial support and an assistant for the summer research of 1998. Peter Vitousek generously offered advice, encouragement and logistical support during all phases of this work, and supplied funds for assistance with arthropod sorting. Lenny Freed provided access to a 4WD vehicle for 3+ years of fieldwork, and Ken Kaneshiro furnished new tires for this vehicle and additional funds to hire a summer field assistant. Jack Ewel provided many honest, thoughtful and pithy comments on proposals and papers, and Bob Kinzie read and commented on every chapter. Dan Blaine valiantly served as the outside member on my committee. Lyman Perry, Bob Cabin, David Foote & Karin SchIappa, Susan Cordell & Pat Hart, Stephen Hight & Nancy Everett, and Keek & Mo Hottendorf offered cheerful hospitality and libations during innumerable Big Island visits. While I lived on Hawai'i VI Island, Dave Strang, Jim Teo, Rena Duhl & Steve Robinow, Aaron Hebshi, Eric VanderWerf, Matt Burt, Laura Rodman, Erin Baumgartner and numerous others hosted my couch surfing on O'ahu. The following individuals identified or confirmed taxonomic designations crucial to this work: Keith T. Arakaki, Miquel A. Arnedo, Manfred Asche, Joe A. Beatty, Todd A. Blackledge, George W. Byers, NealL. Evenhuis, Curtis P. Ewing, Jessica E. Garb, Michael W. Gates, Gary A.P. Gibson, Rosemary G. Gillespie, John T. Huber, Ken Y. Kaneshiro, Bernarr R. Kumashiro, Jim K. Liebherr, Ed 1. Mockford, Steve 1. Montgomery, John S. Noyes, Diana M. Percy, Dan A. Polhemus, David 1. Preston, Neil 1. Reimer, Alastair M.M. Richardson, G. Al Samuelson, Mike E. Schauff, Catherine A. Tauber, and Amy Vandergast. I am grateful for their time and expertise guiding me to understand Hawaiian entomology. Neal Evenhuis and staff at the Bishop Museum provided essential desk space and access to collections. Andy Taylor was my major professor. Andy's door was always open, and I definitely used it. Andy unselfishly provided conscientious advice and technical support on all topics, from statistical analyses, to project development and grant proposals, to grammatical details on papers. Andy consistently went to bat for me when I had no power and no other way. Many sincere thanks. My in-laws, Gary and Clara Trousdale, and my siblings Scott, Amy, and especially Tim helped out in many small and large but very significant ways, and also trusted that my efforts would be worthwhile in the end. My mother, Marietta B. Gruner, was the source and the nourishment of my lifelong pursuit of learning. My mother endured the little invertebrate surprises in my jeans' pockets as a young boy, and logged Vll many frequent flyer miles to help out in Hawai'i. Most importantly, I thank my wife Kristie A. Trousdale who endured my long work hours, extended absences for research travel and conferences, and a move to the Big Island and back again. Kristie supported me emotionally, supported me unconditionally, and believed in me throughout. Finally, my son Adam has infused our home with joy and discovery and taught me about the most important things in life. Only Adam surpasses me in enthusiasm for the arthropods of Hawai'i! Thank you, all! Vlll ABSTRACT The overall aim ofthis research was to weigh the importance oflocal and regional influences in contemporary arthropod biodiversity and community structure. I manipulated vertebrate predation pressure and basal resources in arthropod food webs at a single model field site, and integrated these results into a historical evolutionary framework using a series oftightly constrained sites throughout the Hawaiian Islands. The Hawaiian archipelago forms a linear time series of replicated communities, with ages of volcanic origin varying over four orders ofmagnitude. I sampled free-living arthropods in the canopies of the dominant Hawaiian tree '6hi'a lehua (Myrtaceae: Metrosideros polymorpha) at five sites spanning this gradient on Hawai'i, Moloka'i and Kaua'i. Arthropod abundances and species richness were not related linearly to geological age, but were highest at more productive, intermediate-aged sites. Although historical and evolutionary processes generate diversity at broad scales, local communities were convergent in trophic structure and composition, and resource availability was predictive ofarthropod numbers and richness. I examined the interactive effects ofcarnivores (top-down) and resources (bottom­ up) in a species-rich terrestrial food web. In a 33-mo manipulation, severe soil nutrient limitation on a 120-yr-old lava flow was alleviated by fertilization and combined with bird predator exclusion cages in a randomized block design. Metrosideros growth rate and foliar N increased with fertilization. Detritivores composed the largest fraction of arthropod density and biomass, and bottom-up factors controlled basal trophic levels. Conversely, top-down impacts were apparent but variable, concentrated on large-bodied higher order consumers, and did not cascade to indirectly affect primary producers. One IX previously rare non-indigenous spider species irrupted in the absence of birds, which demonstrated biotic resistance to this invasive species. Other spiders also increased with bird exclusion, but only in fertilized plots. Both treatments influenced species diversity and composition, primarily by altering the relative abundance of species. Foliar pubescence variation altered community composition independently of resource availability. Emergent properties of local food webs corroborated patterns from the gradient study, and reinforced the primacy of local resources as predictors ofstructure in these communities. x TABLE OF CONTENTS ACKNOWLEDGEMENTS v ABSTRACT ix LIST OF TABLES xv LIST OF FIGURES xvii CHAPTER 1: Introduction 1 Trophic Dynamics 2 Bottom-up Processes 4 Top-Down Processes and Trophic Cascades 7 Relative Strengths ofTop-Down and Bottom-Up Forces 8 Regional Scale Processes 9 Metrosideros polymorpha as a Model System for Community Ecology. 11 Overall Aims and Objectives 14 CHAPTER 2: Effects of Productivity and Geological Age on Arboreal Arthropod Community Structure in the Hawaiian Islands 18 Abstract 18 Introduction 19 Methods 22 Study system 22 Arthropod sampling