Responses to Abiotic Conditions

I. The Physical Template

A. Biomes

B. Environmental Variation

C. Disturbances II. Surviving Variable Abiotic Conditions

A. Thermoregulation B Water Balance G Air and Water Chemistry

D. Other Abiotic Factor*


III. ftctors Affecting Dispersal Behavior 45

A. Life History Strategy 45

B. Crowding 45 C Nutritional Status 46

D. Habitat and Resource Condition?» 46

E. Mechanism of Dispersal 47

IV. Responses to Anthropogenic Changes 49 V. Summary 51

3 Resource Acquisition 53

I. Resource Quality 53

A. Resource Requirements 54

B. Variation in Food Quality 55 C Plant Chemical Defenses 5«

D. Arthropod Defenses 65

E. Factors Affecting Expression of Defenses 69

F. Mechanisms for Exploiting Variable Resources 74

II. Resource Acceptability 77

III. Resource Availability SO

A. F oraging Strategies HI

B. Orientation 83 C I-earning 88

IV. Summary 92

4 Resource Allocation 95

I. Resource Budget 95

II. Allocation of Assimilated Resources 97 A. Resource Acquisition 97 a Mating Activity 99

C. Reproductive and Social Behavior li>4

D. Competitive. Defensive, and Mutualistic Behavior 1(J8

III. Efficiency of Resource Use 117 A. Factors Affecting Efficiency 117 a 'IVadcoffs 119

IV. Summary 121



5 Population Systems 125

I. Population Structure 125

A. Density 125

a Dispersion 126

C. Mctapopulation Structure 129

D. Age Structure 130

E. Sex Ratio 132

F. Gcnctic Composition 132

G. Social Insects 136


II. Population Processes 137

A. Natality 137

B. Mortality 138 C Dispersal 141

III. Life History Characteristics 144

IV. Parameter Estimation 146 V. Summary 151

6 Population Dynamics 153

I. Population Fluctuation 154

II. Factors Affecting Pbpulation Size 157 A. Density-Independent Actors 158 a Density-Dependent Factors 163

C. Regulatory Mechanisms 164

III. Models of Population Change 168

A. Exponential and Geometric Models 168

B. Logistic Model 169

C. Complex Models 170

D. Computerized Modcb 171

E. Model Evaluation 174

IV. Summary 176

7 Biogcography 179

I. Geographic Distribution 180

A. Global Patterns 180

B. Regional Patterns 181 C Island Biogcography 182 D. Landscape and Stieam Continuum Patterns 183

II. Spatial Dynamics of Populations 185

A. Expanding Populations 187

B. Metapopulation Dynamics 192

III. Anthropogenic Effects on Spatial Dynamics 195

A. Fragmentation 196

B. Disturbances to Aquatic Ecosystems 199 C Spccics Introductions 200

IV. Conservation Biology 201 V. Models of Spatial Dynamics 204

VI. Summary 208



8 Species Interactions 213

I. Classes of Interactions 213

A. Competition 214

ft Prcdation 219

C Symbiosis 224


II. Factoid A Heeling Interactions 237

A. Abiotic Conditions 237

B. Resource Availability and Distribution 238 C Indirect Effects of Other Spcrics 239

III. Consequence* of Interactions 246

A. Population Regulation 246

B. Community Rcgulntion 246

IV. Summary 247

9 Community Structure 251

I. Approaches to Describing Communities 252

A. Species Diversity 252

B. Spccics Interactions 261

C. Functional Organization 267

II. Patterns of Community Structure 269

A. Global Pattern* 270

B. Biome and Landscape Patterns 271

III. Determinants of Community- Strvcturc 275

A. Habitat Area and Complexity 275

B. 11.ibitnt Stability 277 C Resource Availability 277

D. Species Interactions 278

IV. Summary 281

10 Community Dynamics 283

I. Short-Term Change in Community Structure 284

II. Successional Change in Community Structure 286

A. Patterns of Succession 288

B. Factors Affecting Succcssion 2<M

C. Models of Succession 298 HI. P&leoccology 302

IV. Diversity versus Stability 305

A. Components of Stability 307

B. Stability of Community Variables 308

V. Summary 311



11 Ecosystem Structure and Function 315

I. Ecosystem Structure 316 A. TYophic Structure 317 a Spatial Variability 319

II. Energy Flow 319 A. Primary Productivity 320 a Secondary Productivity 323 C Energy Budgets 324


III. Biogeochemical Cycling 326

A. Abiotic and Biotic Pools 327

B. Major Cycles 328

C. Factors Influencing Cycling Processes 333

IV. Climate Modification 336

V. Fcosysiem Modeling 340 VI. Summary 344

1 2 Herbivory 347

I. Types and Patterns or Herbivory 34«

A. Herbivore Functional Groups 348

B. Measurement of Herbivory 348

C. Spatial and Temporal Patterns of Herbivory 352

II. Effects of Herbivory 358

A. Plant Productivity. Survival and Growth Form 360

B. Community Dynamic* 367 G Water and Nutrient Fluxes 373

D. Effects on Climate and Disturbance Regime 379 HI. Summary 381

13 Pollination, Seed Prédation, and Seed Dispersal 383

I. Types and Pattern* of Pollination 384

A. Pollinator Functional Gtoups 384

B. Measurement of Pollination 387

C. Spatial and Temporal Patterns of f\>llination 388

II. Effects of Pollination 390

III. TVpcs and Patterns of Seed Prédation and Dispersal 394

A. Seed Predator and Disperser Functional Groups 394

B. Measurement of Seed Production and Dispersal 395 C Spatial and Temporal Patterns of Seed Prédation and Dispersal 400

IV. Effects of Seed Prédation and Dispersal 401 V. Summary 403

14 Decomposition and Pedogenesis 405

I. TVpcs and Pattern* of Detritivory and Burrowing 406

A. Dctritivoie and Burrowcr Functional Groups 406

B. Measurement of Detritivory. Burrowing, and Decomposition Rates 408

C. Spatial and Temporal Patterns in Processing of Detritus and Soil 411

II. Effects of Detritivory and Burrowing 416

A. Decomposition and Mineralization 416

B. Soil Structure. Fertility, and Infiltration 425

C. Primary Production and Vegetation Dynamics 430

III. Summary 433

15 Insects as Regulators of Ecosystem Processes 437

I. Development of the Concept 438

II. EcmyMcms as Cybernetic Systems 442 A. Properties of Cybernetic Systems 442


B. Ecosystem Homeostasis 443

C Definition of Stability 445

D. Regulation of Net Primary Production by Biodiversity 448

H. Regulation oi Net Primary Production by Insects 454

III. Summary 459



16 Synthesis 465

I. Summary 466

II. Synthesis 467

III. Applications 469

A. Management of Crop. Forest, and Urban "Pests" 470

B. Conservation-Restoration Ecology 474 C Indicators of Environmental Conditions 475 D. Ecosystem Engineering 476

IV. Critical Issues 476

V. Conclusions 482

fíiblét^rafihy 4S7 Author Index 537 TaxotiiHtik Index 545 Subjn i Index 551 Extended Petmiwumi List 56V


his second edition provides an updated and expanded synthesis of feedbacks and interactions between insects and their environment. A number of recent studies have advanced understanding of feedbacks or provided useful examples of principles. Molecular methods have provided new tools for addressing dispersal and interactions among organisms and have clarified mechanisms of feedback between insect effects on, and responses to, environmental changes. Recent studies of factors controlling energy and nutrient fluxes have advanced understanding and prediction of interactions among organisms and abiotic nutrient pools.

The traditional focus of insect ecology has provided valuable examples of adaptation to environmental conditions and evolution of interactions with other organisms. By contrast, research at the ecosystem level in the last 3 decades has addressed the integral role of herbivores and detritivores in shaping ecosystem conditions and contributing to energy and matter fluxes that influence global processes. This text is intended to provide a modern perspective of insect ecology that integrates these two traditions to approach the study of insect adaptations from an ecosystem context. This integration substantially broadens the scope of insect ecology and contributes to prediction and resolution of the effects of current environmental changes as these affect and are affected by insects.

This text demonstrates how evolutionary and ecosystem approaches complement each other, and is intended to stimulate further integration of these approaches in experiments that address insect roles in ecosystems. Both approaches are necessary to understand and predict the consequences of environmental changes, including anthropogenic changes, for insects and their contributions to ecosystem structure and processes (such as primary productivity, biogeochemical cycling, carbon flux, and community dynamics). Effective management of ecosystem resources depends on evaluation of the complex, often complementary, effects of insects on ecosystem conditions as well as insect responses to changing conditions.

Two emerging needs require the integration of traditional and emerging perspectives of insect roles in ecosystems. First, we are becoming increasingly aware that global environ-

mental changes must be addressed from a global (rather than local) perspective, with emphasis on integrating ecological processes at various levels of resolution and across regional landscapes. Insect population structure, interactions with other species, and effects on ecosystem processes are integral to explaining and mitigating global changes. Second, the changing goals of natural resource management require a shift in emphasis from the traditional focus on insect-plant interactions and crop "protection" to an integration of ecosystem components and processes that affect sustainability of ecosystem conditions and products. Integrated pest management (IPM) is founded on such ecological principles.

The hierarchical model, familiar to ecosystem ecologists and used in this text, focuses on linkages and feedbacks among individual, population, community, and ecosystem properties. This model contributes to integration of evolutionary and ecosystem approaches by illustrating how properties at higher levels of resolution (e.g., the community or ecosystem) contribute to the environment perceived at lower levels (e.g., populations and individuals) and how responses at lower levels contribute to properties at higher levels of this hierarchy. Some overlap among sections and chapters is necessary to emphasize linkages among levels. Where possible, overlap is minimized through cross-referencing.

A number of colleagues have contributed enormously to my perspectives on insect and ecosystem ecology. I am especially grateful to J.T. Callahan, J.-T. Chao, S. L. Collins, R. N. Coulson, D. A. Crossley, Jr., R. Dame, D. A. Distler, L. R. Fox, J. F. Franklin, F. B. Golley, J. R. Gosz, M. D. Hunter, F. Kozár, M. D. Lowman, G. L. Lovett, H.-K. Luh, J. C. Moore, E. P. Odum, H. T. Odum, D. W. Roubik, T. R. Seastedt, D. J. Shure, P. Turchin, R. B. Waide, W. G. Whitford, R. G. Wiegert, M. R. Willig, and W.-J. Wu for sharing ideas, data, and encouragement. I also have benefited from collaboration with colleagues at Louisiana State University and Oregon State University and associated with U.S. Long Term Ecological Research (LTER) sites, International LTER projects in Hungary and Taiwan, the Smithsonian Tropical Research Institute, Wind River Canopy Crane Research Facility, Teakettle Experimental Forest, USDA Forest Service Demonstration of Ecosystem Management Options (DEMO) Project, USDA Western Regional Project on Bark Beetle-Pathogen Interactions, and the National Science Foundation. L. R. Fox, T. R. Seastedt, and M. R. Willig reviewed drafts of the previous edition. Several anonymous reviewers provided useful comments addressed in this edition. I also am indebted to C. Schowalter for encouragement and feedback. K. Sonnack, B. Siebert and H. Furrow at Elsevier provided valuable editorial assistance. I am, of course, solely responsible for the selection and organization of material in this book.

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