The Effect of Biotic and Abiotic Forces on Species Richness Peter J.T. White Faculty of Science, Department of Biology McGill University Montréal, Québec, Canada A thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Doctor of Philosophy © Peter J.T. White, 2011 1 TABLE OF CONTENTS Table of Contents………………………………………………………………………………………………..….. 2 List of Tables………………………………………………………………………….….……………………………. 5 List of Figures……………………………………………………………………………………….…….…….…….. 8 List of Appendices……………………………………………………………………………………………………. 13 Preface………………………………………………………………………………………………………………….… 14 Thesis Format and Style…………………………………………………………………………………… 14 Contribution of Co-Authors……………………………………………………………………………… 15 Original Contributions to Knowledge……………………………………………………………….. 17 References………………………………………………………………………………………………………. 21 Acknowledgements…………………………………………………………………………………………. 23 Thesis Abstract………………………………………………………………………………………………………… 26 Résumé……………………………………………………………………………………………………………………. 28 General Introduction……………………………………………………………………………………………….. 30 References……………………………………………………………………………………………….……… 45 Chapter 1: Detecting Changes in Forest Floor Habitat after Canopy Disturbances…… 53 Abstract……………………..……………………………………………………………………………………. 54 Introduction…………………………………………………………………………………………………….. 55 Local Consequences of Damage……………………………………………………………….. 55 Landscape and Regional Investigations……………………………………………….…… 56 Habitat Implications of Ice Storms………………………………………………………….… 56 Using Remote Sensing to Measure Habitat Change…………………….…………… 58 Objective………………………………………………………………………………….……………… 59 Method……………………………………………………………………………………………….…………… 59 Study Area………………………………………………………………………………………..……… 59 Satellite Imagery Processing…………………………………………………………………….. 60 VI Calculation…………………………………………………………………………………………… 61 Predicting the Spatial Pattern of CWD Influx……………………………………………. 63 Independent Validation of CWD Predictions…………………………………….……… 64 Methods Evaluation……………………………………………………………………………….… 65 Categorizing CWD Habitat………………………………………………………………………… 66 Results……………………………………………………………………………………………………………… 67 Performance of VIs for Predicting CWD Influx……………………………………..…… 67 Independent Validation of CWD Predictions………………………………….………… 68 Categorization of CWD Influx into Different Habitat Types………………….…… 68 Methods Evaluation………………………………………………………………………….……… 69 Discussion……………………………………………………………………………………………………….. 69 Accuracy of VIs in Predicting Spatial Pattern of Damage…………………..……… 69 CWD Benefits for Mont St Hilaire Species…………………………………………..….… 71 The Benefits of Different Habitat Types for Insects……………………………..…… 72 CWD Influx and Species Movements……………………………………………………..… 74 Conclusion………………………………….……………………………………………………………. 76 Acknowledgements……………………………………………………………….………………………… 77 References………………………………………………………………………………………………………. 78 Figures……………………………………………………………………………………………………………… 89 Tables……………………………………………………………………………………………………………… 92 2 Linking Statement 1………………………………………………………………………………….………..…… 96 Chapter 2: Human-Disturbance and Caterpillars in Managed Forest Fragments.….…. 97 Abstract……………………………………………………………………………………………………….….. 98 Introduction……………………………………………………………………………………………….……. 99 Trailside Habitat in Forests………………………………………………………………………. 99 An Analogy of Forest Edge Habitat…………………………………………………………... 101 Hypotheses……………………………………………………………….….…….….….….………… 102 Method……………………………………………………………………………………………………………. 103 Study Area……………………………………………………………………………………………….. 103 Trail Index Calculation……………………………………………………………………………… 106 Caterpillar Surveying and Identification…………………………………………………… 107 Site Host Plant Availability……………………………………………………………………….. 108 Statistical Analysis……………………………………………………………………………………. 109 Results…………………………………………………………………………………………………………….. 110 Trail Index and Host Plant Availability……………………………………………………… 110 Random Versus Non-Random Distribution of Caterpillar Species…………….. 111 Discussion……………………………………………………………………………………………………….. 112 Possible Mechanisms of Negative Relationship……………………………………….. 112 Trails Versus Edges…………………………………………………………………………………… 114 Conclusion……………………………………………………………………………………………….. 116 Acknowledgements………………………………………………………………………………….……… 117 References………………………………………………………………………………………………………. 118 Figures……………………………………………………………………………………………………….……. 131 Tables……………………………………………………………………………………………………………… 134 Linking Statement 2………………………………………………………………………………………………… 136 Chapter 3: Testing Two Methods that Relate Herbivorous Insects to Host Plants….... 137 Abstract…………………………………………………………………………………………………………… 138 Introduction…………………………………………………………………………………………………….. 140 Overlooked in Conservation Planning…………………………………………………..….. 140 The Relationship between Hosts and Lepidoptera………………………………..…. 141 Methods………………………………………………………………………………..….….….….…....…… 144 Study Area…………………………………………………………………………..…………………… 144 Caterpillar Survey and Identification………………………………………………………… 146 Controlling for Habitat Disturbance..…………………………………………………..…… 147 Analyses…………………………………………………………………………………………………… 147 Host Plant and Caterpillar Relationships..……………………………….…….….….….. 149 Testing Host Plant-Specific Preferences………………………………….…….….….….. 149 Results………………………………………………………………………………………………………….…. 150 Caterpillar Sampling…………………………………………………………………………………. 150 Host Plant and Caterpillar Relationships………………………………………………….. 151 CAPIr and CAPIa…………..………………………………………………………………………….. 151 Host Plant Importance Relative to Trail Index………………………………………….. 152 Discussion……………………………………………………………………………………………………..… 153 Biodiversity and Conservation….….….…………………………………………………….… 153 Low Richness and Abundance in Invasive Trees……………………………………….. 154 Mechanisms…..….….….….….….….……………………………………………….…..…..…….. 157 Conclusion……………………………………………………………………………………………..… 159 3 Acknowledgements……………………………………………………………………………………..….. 161 References………………………………………………………………………………………………….…… 162 Figures………………………………………………………………………………………………………..…… 172 Tables………………………………………………………………………………………………………….…… 177 Linking Statement 3………………………………………………………………………………………………… 181 Chapter 4: Intra-Seasonal Relationships between Insect Herbivores and their Hosts. 182 Abstract……………………………………………………………………………………………………….….. 183 Introduction………………………………………………………………………………………………….…. 184 Bottom-Up Effects: Foliar Quality.….….……………………….…….….…………………. 184 Bottom-Up Effects: Foliar Toxins.….….….….….….….….….….………………………… 186 Top-Down Effects.….….….….….….….….….….….….….….….….….….….…………….… 187 Current Gaps in Foliar Quality Research.….….….………….…….….…………………. 188 Tri-Trophic Relationships……………….….….….….….….….….…….….…………………. 191 Objective…………………………………………………………………………………………………. 192 Methods……………………………………………………………………………………………………….…. 193 Study Area…………………………………………………………………………………………….…. 193 Caterpillar Survey and Identification………………………………………………………... 195 Measuring the Bottom-Up Effect…………………………..…..….……………….…..…... 195 Measuring the Top-Down Effect…………………………….….….……………….…..…... 196 Analysis.….….….….….….….….….….….….………………….……………..….……….…..…... 198 Methodological Assumptions…………………………………………………………………... 199 Results……………………………………………………………………………………………….……………. 200 Bottom-Up Foliar Quality……………………….………………………………………………… 201 Top-Down Pressure…………………………………………………………………………………. 201 Seasonality of Bottom-Up Effects.….….…………………………………………………….. 201 Tri-Trophic Relationships.….….….….….…………………….….….……………….…..…... 203 Discussion…………………………………………………………………………………………….….….….. 204 Bottom-Up: Foliar Quality………………….…………………………………….…….………… 204 Bottom-Up: Toxins……………………………..….….……………………………….…………... 207 Top Down: Parasitoids…………………………………………………………………….…....… 208 Conclusion…………………………………………………………………………………….……….… 210 Acknowledgements……………………………………………………………………………………….… 211 References…………………………………………………………………………………………………….… 212 Figures…………………………………………………………………………………………………………….. 223 Tables……………………………………………………………………………………………………………… 228 General Conclusion……………………………………………………………………………………………….… 232 References……………………………………………………………………………………………………………... 237 Appendices……………………………………………………………………………………………………………… 239 4 LIST OF TABLES CHAPTER 1: Table 1 Landsat-5 satellite imagery used in calculation of vegetation indices for Mont St. Hilaire in 1996 and 1998. Table 2 Vegetation Indices (VIs) used to calculate forest damage after the 1998 ice storm at Mont St. Hilaire. The VIs incorporated four wavelengths of light: blue (450 – 520 nm), green (520 – 600 nm), red (630 – 690 nm) and near infrared (NIR, 760 – 900 nm). Table 3 The data for each regression model were split into random training and validation datasets (80/20 ratio, 66/16 plots) to create ten cross validation trials for each Vegetation Index. The R2 fit of each validation dataset is given respective of the regression coefficient and intercept calculated in its training dataset. NDVI provides the best for both training and validation datasets (R2 = 0.20 and 0.37, respectively). CHAPTER 2: Table 1 Trail Index is a consistent negative predictor of caterpillar abundance and caterpillar species richness both across and within study sites.Host plant availability is rarely significantly linked to caterpillar species abundance or richness, only explaining a large degree of caterpillar variance at Mont Shefford. Near-significant (*) and significant (**) p-values are marked. 5 CHAPTER 3: Table 1The relationship between host plants and caterpillars shows that (a) host plant (Shannon’s) diversity is a significant descriptor of caterpillar (Shannon’s) diversity when Trail disturbance is accounted 2 for (total model adjusted