FM-P088772.qxd 1/24/06 11:11 AM Page xi PREFACE his second edition provides an updated and expanded synthesis of feedbacks and interactions between insects and their environment. A number of recent studies have T advanced understanding of feedbacks or provided useful examples of principles. Mo- lecular 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 nutri- ent 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 her- bivores 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 per- spective 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 envi- ronmental 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 pro- ductivity, biogeochemical cycling, carbon flux, and community dynamics). Effective manage- ment 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- xi FM-P088772.qxd 1/24/06 11:11 AM Page xii xii PREFACE 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 man- agement 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 resolu- tion (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 Foun- dation. 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 feed- back. K. Sonnack, B. Siebert and H. Furrow at Elsevier provided valuable edito- rial assistance. I am, of course, solely responsible for the selection and organization of material in this book. 001-P088772.qxd 1/24/06 10:31 AM Page 1 1 Overview I. Scope of Insect Ecology II. Ecosystem Ecology A. Ecosystem Complexity B. The Hierarchy of Subsystems C. Regulation III. Environmental Change and Disturbance IV. Ecosystem Approach to Insect Ecology V. Scope of This Book INSECTS ARE THE DOMINANT GROUP OF ORGANISMS ON EARTH, IN terms of both taxonomic diversity (>50% of all described species) and ecological function (E. Wilson 1992) (Fig. 1.1). Insects represent the vast majority of species in terrestrial and freshwater ecosystems and are important components of near- shore marine ecosystems as well. This diversity of insect species represents an equivalent variety of adaptations to variable environmental conditions. Insects affect other species (including humans) and ecosystem parameters in a variety of ways. The capacity for rapid response to environmental change makes insects useful indicators of change, major engineers and potential regulators of ecosys- tem conditions, and frequent competitors with human demands for ecosystem resources or vectors of human and animal diseases. Insects also play critical roles in ecosystem function.They represent important food resources or disease vectors for many other organisms, including humans, and they have the capacity to alter rates and directions of energy and matter fluxes (e.g., as herbivores, pollinators, detritivores, and predators) in ways that potentially affect global processes. In some ecosystems, insects and other arthro- pods represent the dominant pathways of energy and matter flow, and their bio- mass may exceed that of the more conspicuous vertebrates (e.g., Whitford 1986). Some species are capable of removing virtually all vegetation from a site. They affect, and are affected by, environmental issues as diverse as ecosystem health, air and water quality, genetically modified crops, disease epidemiology, frequen- cy and severity of fire and other disturbances, control of invasive exotic species, land use, and climate change. Environmental changes, especially those resulting from anthropogenic activities, affect abundances of many species in ways that alter ecosystem and, perhaps, global processes. A primary challenge for insect ecologists is to place insect ecology in an ecosystem context that represents insect effects on ecosystem properties, as well 1 001-P088772.qxd 1/24/06 10:31 AM Page 2 2 1. OVERVIEW Insects 800,000 751,000 700,000 600,000 500,000 400,000 Plants 300,000 275,300 Number of Species Other Other arthropods 200,000 invertebrates 123,400 106,300 Fungi Viruses 100,000 69,000 Chordates Protozoa and 42,300 30,800 bacteria 5,800 0 FIG. 1.1 Distribution of described species within major taxonomic groups. Species numbers for insects, bacteria, and fungi likely will increase greatly as these groups become better known. Data from E. O. Wilson (1992). as the diversity of their adaptations and responses to environmental conditions. Until relatively recently, insect ecologists have focused on the evolutionary sig- nificance of insect life histories and interactions with other species, especially as pollinators, herbivores, and predators (Price 1997). This focus has yielded much valuable information about the ecology of individual species and species associ- ations and provides the basis for pest management or recovery of threatened and endangered species. However, relatively little attention has been given to the important role of insects as ecosystem engineers, other than to their effects on vegetation (especially commercial crop) or animal (especially human and live- stock) dynamics. Ecosystem ecology has advanced rapidly during the past 50 years. Major strides have been made in understanding how species interactions and environ- mental conditions affect rates of energy and nutrient fluxes in different types of ecosystems, how these provide free services (such as air and water filtration), and how environmental conditions both affect and reflect community structure (e.g., Costanza et al. 1997, Daily 1997, H. Odum 1996). Interpreting the responses of a diverse community to multiple interacting environmental factors in integrated ecosystems requires new approaches, such as multivariate statistical analysis and modeling (e.g.,