SPATIAL AND TEMPORAL EFFECTS OF FIRE ON INSECT HERBIVORE COMMUNITY STRUCTURE By TANIA N. KIM A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2006 1 Copyright 2006 by Tania N. Kim 2 ACKNOWLEDGMENTS First, I thank my committee members, Bob Holt, Scott Robinson, and Emilio Bruna, for reading my thesis and providing critical feedback at every stage of my research study. I also thank the scientists at Archbold Biological Station, particularly Hilary Swain, Eric Menges, Carl Weekley, Mark Deyrup, Patrick Bohlen, Adam Peterson, Jenny Schafer, and Marcia Rickey, for logistical support and encouragement. In addition, I thank the Bruna lab for allowing me to use their facilities while on-campus and I thank Pedro Mendez for aiding me with laboratory work. This project was funded by various sources, such as the Garden Club of America, the Florida Native Plant Society, and the Department of Zoology. Finally, I thank my family and friends for their love and encouragement, and of course, I thank Brian J. Spiesman and Reginald P. Doggie for their constant love, patience, humor, and emotional support over the past 6 years. 3 TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................3 LIST OF TABLES...........................................................................................................................6 LIST OF FIGURES .........................................................................................................................8 CHAPTER 1 INTRODUCTION ..................................................................................................................13 Conceptual Model...................................................................................................................15 The Lake Wales Scrub: A Fire-Dominated Ecosystem..........................................................16 Study Site................................................................................................................................18 Study Organisms.....................................................................................................................19 Insect Herbivores....................................................................................................................20 Overview.................................................................................................................................20 2 EFFECTS OF FIRE ON INSECT HERBIVORE COMMUNITY STRUCTURE................23 Introduction.............................................................................................................................23 Methods ..................................................................................................................................27 Plot Establishment and Sampling Regime ......................................................................28 Leaf traits and Tannin Analyses......................................................................................29 Vegetation Sampling .......................................................................................................30 Fire Regime and Landscape Heterogeneity.....................................................................30 Arthropod Identification..................................................................................................31 Data Analysis...................................................................................................................31 Differences in insect community structure...............................................................31 Determinants of insect community structure ...........................................................32 Results.....................................................................................................................................33 Mixed Models..................................................................................................................33 Discriminant Analyses.....................................................................................................35 Principal Component Analyses .......................................................................................35 Path Analysis...................................................................................................................36 Effects of fire on leaf, plant, and plot architecture...................................................36 Effects of fire on insect communities.......................................................................37 Discussion...............................................................................................................................37 Herbivores of Q. chapmanii ............................................................................................39 Herbivores of Q. inopina.................................................................................................40 Herbivores of Q. geminata ..............................................................................................42 Concluding Comments ....................................................................................................42 3 SPATIAL AND TEMPORAL EFFECTS OF FIRE ON PLANT DAMAGE IN THE FLORIDA SCRUB.................................................................................................................81 4 Introduction.............................................................................................................................81 Methods ..................................................................................................................................85 Plot Establishment and Sampling Regime ......................................................................86 Data Analysis...................................................................................................................88 Mapping damage patterns ........................................................................................88 Path analysis.............................................................................................................88 Results.....................................................................................................................................89 Inverse Distance Weighting Maps...................................................................................91 Factors Influencing Leaf Tissue Damage........................................................................92 Discussion...............................................................................................................................92 4 CONCLUSIONS ..................................................................................................................117 LIST OF REFERENCES.............................................................................................................119 BIOGRAPHICAL SKETCH .......................................................................................................128 5 LIST OF TABLES Table page 2-1 Variables used in PCA for path analysis............................................................................44 2-2 The number of arthropods by order sustained on the 3 species of oaks dominant in the Florida scrub. ...............................................................................................................46 2-3 Number of arthropod herbivores found on the three dominant oak species in the Florida scrub. .....................................................................................................................47 2-4 Mixed model results comparing insect herbivore abundance on three dominant oaks (Q. chapmanii, Q. geminata, and Q. inopina) in the Florida scrub. ..................................49 2-5 Mixed model results comparing insect herbivore richness on three dominant oaks (Q. chapmanii, Q. geminata, and Q. inopina) in the Florida scrub. ........................................50 2-6 Mixed model results comparing Simpson’s diversity of insect herbivores on three dominant oaks (Q. chapmanii, Q. geminata, and Q. inopina) in the Florida scrub...........51 2-7 MANOVA results examining differences in the abundance of herbivores as a function of time since fire, season, and oak species. .........................................................52 2-8 Results from discriminant analysis of insect species grouped according to oak species................................................................................................................................54 2-9 Structure matrix from discriminant analysis......................................................................55 2-10 Chi-square statistic results comparing default model with a fully saturated model. .........57 2-11 Direct and indirect effects of fire on insect herbivore abundance. ....................................58 3-1 Differences in leaf damage as a function of seasonal stage and time-since-fire. ..............98 3-2 Differences in the average number of leaves consumed per plant as a function of seasonal stage and time-since-fire .....................................................................................99 3-3 Multi-scale patterns of plant damage as a function of stand age .....................................100 3-4 Variation in the magnitude of leaf