ECOLOGY. Sinauer Associates, Inc. Sunderland, Massachusetts

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1 ECOLOGY Second Edition MICHAEL L. CAIN Bowdoin College WILLIAM D. BOWMAN University of Colorado SALLY D. HACKER Oregon State University Sinauer Associates, Inc. Sunderland, Massachusetts

2 Brief Contents 1 The Web of Life 2 UNIT 1 Organisms and Their Environment 2 The Physical Environment 22 3 The Biosphere 49 4 Coping with Environmental Variation: Temperature and Water 81 5 Coping with Environmental Variation: Energy Evolution and Ecology 132 UNIT 2 Populations 7 Life History Population Distribution and Abundance Population Growth and Regulation Population Dynamics 221 UNIT 3 Interactions among Organisms 11 Competition Predation and Herbivory Parasitism Mutualism and Commensalism 305 UNIT 4 Communities 15 The Nature of Communities Change in Communities Biogeography Species Diversity in Communities 388 UNIT 5 Ecosystems 19 Production Energy Flow and Food Webs Nutrient Supply and Cycling 452 UNIT 6 Applied and Large-Scale Ecology 22 Conservation Biology Landscape Ecology and Ecosystem Management Global Ecology 525

3 Contents CHAPTER 1 The Web of Life 2 Deformity and Decline in Amphibian Populations: A Case Study 2 Introduction 3 CONCEPT 1.1 Events in the natural world are interconnected. 3 Connections in Nature 3 CONCEPT 1.2 Ecology is the scientific study of interactions between organisms and their environment. 8 Ecology 8 CONCEPT 1.3 Ecologists evaluate competing hypotheses about natural systems with observations, experiments, and models. 13 Answering Ecological Questions 13 ECOLOGICAL TOOLKIT 1.1 Designing Ecological Experiments 16 A CASE STUDY REVISITED Deformity and Decline in Amphibian Populations 17 CONNECTIONS IN NATURE Mission Impossible? 18 UNIT 1 Organisms and Their Environment CHAPTER 2 The Physical Environment 22 Climatic Variation and Salmon Abundance: A Case Study 22 Introduction 23 CONCEPT 2.1 Climate is the most fundamental component of the physical environment. 23 Climate 23 CONCEPT 2.2 Winds and ocean currents result from differences in solar radiation across Earthí s surface. 26 Atmospheric and Oceanic Circulation 26 CONCEPT 2.3 Large scale atmospheric and oceanic circulation patterns establish global patterns of temperature and precipitation. 31 Global Climatic Patterns 31 CONCEPT 2.4 Regional climates reflect the influence of the distribution of oceans and continents, mountains, and vegetation. 34 Regional Climatic Influences 34 CONCEPT 2.5 Seasonal and long term climatic variation are associated with changes in Earthí s position relative to the sun. 37 Climatic Variation over Time 37 CONCEPT 2.6 Salinity, acidity, and oxygen concentrations are major determinants of the chemical environment. 42 The Chemical Environment 42 A CASE STUDY REVISITED Climatic Variation and Salmon Abundance 45 CONNECTIONS IN NATURE Climatic Variation and Ecology 47

4 xvi Contents CHAPTER 3 The Biosphere 49 The American Serengeti Twelve Centuries of Change in the Great Plains: A Case Study 49 Introduction 50 CONCEPT 3.1 Terrestrial biomes are characterized by the growth forms of the dominant vegetation. 50 Terrestrial Biomes 50 CONCEPT 3.2 Biological zones in freshwater ecosystems are associated with the velocity, depth, temperature, clarity, and chemistry of the water. 68 Freshwater Biological Zones 68 CONCEPT 3.3 Marine biological zones are determined by ocean depth, light availability, and the stability of the bottom substrate. 70 Marine Biological Zones 70 A CASE STUDY REVISITED The American Serengeti Twelve Centuries of Change in the Great Plains 76 CONNECTIONS IN NATURE Long-Term Ecological Research 77 CHAPTER 4 Coping with Environmental Variation: Temperature and Water 81 Frozen Frogs: A Case Study 81 Introduction 82 CONCEPT 4.1 Each species has a range of environmental tolerances that determines its potential geographic distribution. 82 Response to Environmental Variation 82 CONCEPT 4.2 The temperature of an organism is determined by exchanges of energy with the external environment. 85 Variation in Temperature 85 CONCEPT 4.3 The water balance of an organism is determined by exchanges of water and solutes with the external environment. 94 Variation in Water Availability 94 A CASE STUDY REVISITED Frozen Frogs 101 CONNECTIONS IN NATURE Desiccation Tolerance, Body Size, and Rarity 102 CHAPTER 5 Coping with Environmental Variation: Energy 106 Toolmaking Crows: A Case Study 106 Introduction 107 CONCEPT 5.1 Organisms obtain energy from sunlight, from inorganic chemical compounds, or through the consumption of organic compounds. 107 Sources of Energy 107 CONCEPT 5.2 Radiant and chemical energy captured by autotrophs is converted into stored energy in carbon carbon bonds. 109 Autotrophy 109 CONCEPT 5.3 Environmental constraints have resulted in the evolution of biochemical pathways that improve the efficiency of photosynthesis. 113 Photosynthetic Pathways 113 CONCEPT 5.4 Heterotrophs have adaptations for acquiring and assimilating energy efficiently from a variety of organic sources. 119 Heterotrophy 119 ECOLOGICAL TOOLKIT 5.1 Stable Isotopes 120 A CASE STUDY REVISITED Toolmaking Crows 128 CONNECTIONS IN NATURE Tool Use: Adaptation or Learned Behavior? 129 CHAPTER 6 Evolution and Ecology 132 Trophy Hunting and Inadvertent Evolution: A Case Study 132 Introduction 133 CONCEPT 6.1 Evolution can be viewed as genetic change over time or as a process of descent with modification. 133 What Is Evolution? 133 CONCEPT 6.2 Natural selection, genetic drift, and gene flow can cause allele frequencies in a population to change over time. 136 Mechanisms of Evolution 136 CONCEPT 6.3 Natural selection is the only evolutionary mechanism that consistently causes adaptive evolution. 140 Adaptive Evolution 140 CONCEPT 6.4 Long-term patterns of evolution are shaped by large-scale processes such as speciation, mass extinction, and adaptive radiation. 144 The Evolutionary History of Life 144 CONCEPT 6.5 Ecological interactions and evolution exert a profound influence on one another. 148 Joint Effects of Ecology and Evolution 148 A CASE STUDY REVISITED Trophy Hunting and Inadvertent Evolution 151 CONNECTIONS IN NATURE The Human Impact on Evolution 151

5 Contents xvii UNIT 2 Populations CHAPTER 7 Life History 156 Nemo Grows Up: A Case Study 156 Introduction 157 CONCEPT 7.1 Life history patterns vary within and among species. 157 Life History Diversity 157 CONCEPT 7.2 Reproductive patterns can be classified along several continua. 164 Life History Continua 164 CONCEPT 7.3 There are trade-offs between life history traits. 167 Trade-Offs 167 CONCEPT 7.4 Organisms face different selection pressures at different life cycle stages. 170 Life Cycle Evolution 170 A CASE STUDY REVISITED Nemo Grows Up 173 CONNECTIONS IN NATURE Territoriality, Competition, and Life History 174 CHAPTER 8 Population Distribution and Abundance 177 From Kelp Forest to Urchin Barren: A Case Study 177 Introduction 178 CONCEPT 8.1 Populations are dynamic entities that vary in size over time and space. 178 Populations 178 CONCEPT 8.2 The distributions and abundances of organisms are limited by habitat suitability, historical factors, and dispersal. 182 Distribution and Abundance 182 CONCEPT 8.3 Many species have a patchy distribution of populations across their geographic range. 186 Geographic Range 186 CONCEPT 8.4 The dispersion of individuals within a population depends on the location of essential resources, competition, dispersal, and behavioral interactions. 188 Dispersion within Populations 188 CONCEPT 8.5 Population abundances and distributions can be estimated with area-based counts, distance methods, mark recapture studies, and niche modeling. 190 Estimating Abundances and Distributions 190 ECOLOGICAL TOOLKIT 8.1 Estimating Abundance 191 A CASE STUDY REVISITED From Kelp Forest to Urchin Barren 194 CONNECTIONS IN NATURE From Urchins to Ecosystems 196 CHAPTER 9 Population Growth and Regulation 199 Human Population Growth: A Case Study 199 Introduction 200 CONCEPT 9.1 Life tables show how survival and reproductive rates vary with age, size, or life cycle stage. 201 Life Tables 201 CONCEPT 9.2 Life table data can be used to project the future age structure, size, and growth rate of a population. 204 Age Structure 204 CONCEPT 9.3 Populations can grow exponentially when conditions are favorable, but exponential growth cannot continue indefinitely. 207 Exponential Growth 207 ECOLOGICAL TOOLKIT 9.1 Estimating Population Growth Rates in a Threatened Species 208 CONCEPT 9.4 Population size can be determined by density-dependent and density-independent factors. 211 Effects of Density 211 CONCEPT 9.5 The logistic equation incorporates limits to growth and shows how a population may stabilize at a maximum size, the carrying capacity. 214 Logistic Growth 214 A CASE STUDY REVISITED Human Population Growth 216 CONNECTIONS IN NATURE Your Ecological Footprint 217

6 xviii Contents CHAPTER 10 Population Dynamics 221 A Sea in Trouble: A Case Study 221 Introduction 222 CONCEPT 10.1 Populations exhibit a wide range of growth patterns, including exponential growth, logistic growth, fluctuations, and regular cycles. 223 Patterns of Population Growth 223 CONCEPT 10.2 Delayed density dependence can cause populations to fluctuate in size. 226 Delayed Density Dependence 226 CONCEPT 10.3 The risk of extinction increases greatly in small populations. 229 Population Extinction 229 CONCEPT 10.4 Many species have a metapopulation structure in which sets of spatially isolated populations are linked by dispersal. 234 Metapopulations 234 A CASE STUDY REVISITED A Sea in Trouble 237 CONNECTIONS IN NATURE From Bottom to Top, and Back Again 237 UNIT 3 Interactions among Organisms CHAPTER 11 Competition 242 Competition in Plants That Eat Animals: A Case Study 242 Introduction 243 CONCEPT 11.1 Competition occurs between individuals of two species that share the use of a resource that limits their growth, survival, or reproduction. 243 Competition for Resources 243 CONCEPT 11.2 Competition, whether direct or indirect, can limit the distributions and abundances of competing species. 246 General Features of Competition 246 CONCEPT 11.3 Competing species are more likely to coexist when they use resources in different ways. 249 Competitive Exclusion 249 ECOLOGICAL TOOLKIT 11.1 Isocline Analyses 252 CONCEPT 11.4 The outcome of competition can be altered by environmental conditions, species interactions, disturbance, and evolution. 254 Altering the Outcome of Competition 254 A CASE STUDY REVISITED Competition in Plants That Eat Animals 257 CONNECTIONS IN NATURE The Paradox of Diversity 258 CHAPTER 12 Predation and Herbivory 262 Snowshoe Hare Cycles: A Case Study 262 Introduction 263 CONCEPT 12.1 Most predators have broad diets, whereas a majority of herbivores have relatively narrow diets. 264 Predators and Herbivores 264 CONCEPT 12.2 Organisms have evolved a wide range of adaptations that help them obtain food and avoid being eaten. 266 Adaptations to Exploitative Interactions 266 CONCEPT 12.3 Predation and herbivory can affect ecological communities greatly, in some cases causing a shift from one community type to another. 271 Effects of Exploitation on Communities 271 CONCEPT 12.4 Population cycles can be caused by exploitative interactions. 275 Exploitation and Population Cycles 275 A CASE STUDY REVISITED Snowshoe Hare Cycles 278 CONNECTIONS IN NATURE From Fear to Hormones to Population Dynamics 280 CHAPTER 13 Parasitism 283 Enslaver Parasites: A Case Study 283 Introduction 284

7 Contents xix CONCEPT 13.1 Parasites typically feed on only one or a few host individuals. 285 Parasite Natural History 285 CONCEPT 13.2 Hosts have adaptations for defending themselves against parasites, and parasites have adaptations for overcoming host defenses. 287 Defenses and Counterdefenses 287 CONCEPT 13.3 Host and parasite populations can evolve together, each in response to selection pressure imposed by the other. 290 Parasite Host Coevolution 290 CONCEPT 13.4 Parasites can reduce the sizes of host populations and alter the outcomes of species interactions, thereby causing communities to change. 293 Ecological Effects of Parasites 293 CONCEPT 13.5 Simple models of host pathogen dynamics suggest ways to control the establishment and spread of diseases. 297 Dynamics and Spread of Diseases 297 A CASE STUDY REVISITED Enslaver Parasites 301 CONNECTIONS IN NATURE From Chemicals to Evolution and Ecosystems 302 CHAPTER 14 Mutualism and Commensalism 305 The First Farmers: A Case Study 305 Introduction 306 CONCEPT 14.1 In positive interactions, neither species is harmed and the benefits of the interaction are greater than the costs for at least one species. 306 Positive Interactions 306 CONCEPT 14.2 Each partner in a mutualistic interaction acts in ways that serve its own ecological and evolutionary interests. 313 Characteristics of Mutualism 313 CONCEPT 14.3 Positive interactions affect the abundances and distributions of populations as well as the composition of ecological communities. 316 Ecological Consequences of Positive Interactions 316 A CASE STUDY REVISITED The First Farmers 319 CONNECTIONS IN NATURE From Mandibles to Nutrient Cycling 320 UNIT 4 Communities CHAPTER 15 The Nature of Communities 324 Killer Algae! : A Case Study 324 Introduction 325 CONCEPT 15.1 Communities are groups of interacting species that occur together at the same place and time. 325 What Are Communities? 325 CONCEPT 15.2 Species diversity and species composition are important descriptors of community structure. 328 Community Structure 328 CONCEPT 15.3 Communities can be characterized by complex networks of direct and indirect interactions that vary in strength and direction. 333 Interactions of Multiple Species 333 ECOLOGICAL TOOLKIT 15.1 Measurements of Interaction Strength 337 A CASE STUDY REVISITED Killer Algae! 340 CONNECTIONS IN NATURE Stopping Invasions Requires Commitment 340 CHAPTER 16 Change in Communities 343 A Natural Experiment of Mountainous Proportions: A Case Study 343 Introduction 344 CONCEPT 16.1 Agents of change act on communities across all temporal and spatial scales. 345 Agents of Change 345 CONCEPT 16.2 Succession is the process of change in species composition over time as a result of abiotic and biotic agents of change. 347 Basics of Succession 347

8 xx Contents CONCEPT 16.3 Experimental work on succession shows its mechanisms to be diverse and contextdependent. 351 Mechanisms of Succession 351 CONCEPT 16.4 Communities can follow different successional paths and display alternative states. 357 Alternative Stable States 357 A CASE STUDY REVISITED A Natural Experiment of Mountainous Proportions 359 CONNECTIONS IN NATURE Primary Succession and Mutualism 361 CHAPTER 17 Biogeography 364 The Largest Ecological Experiment on Earth: A Case Study 364 Introduction 365 CONCEPT 17.1 Patterns of species diversity and distribution vary at global, regional, and local spatial scales. 365 Biogeography and Spatial Scale 365 CONCEPT 17.2 Global patterns of species diversity and composition are influenced by geographic area and isolation, evolutionary history, and global climate. 371 Global Biogeography 371 CONCEPT 17.3 Regional differences in species diversity are influenced by area and distance, which determine the balance between immigration and extinction rates. 378 Regional Biogeography 378 ECOLOGICAL TOOLKIT 17.1 Species Area Curves 380 A CASE STUDY REVISITED The Largest Ecological Experiment on Earth 384 CONNECTIONS IN NATURE Tropical Rainforest Diversity Benefits Humans 385 CHAPTER 18 Species Diversity in Communities 388 Powered by Prairies? Biodiversity and Biofuels: A Case Study 388 Introduction 389 CONCEPT 18.1 Species diversity differs among communities due to variation in regional species pools, abiotic conditions, and species interactions. 389 Community Membership 389 CONCEPT 18.2 Resource partitioning among the species in a community reduces competition and increases species diversity. 393 Resource Partitioning 393 CONCEPT 18.3 Processes such as disturbance, stress, predation, and positive interactions can mediate resource availability, thus promoting species coexistence and species diversity. 396 Processes That Promote Coexistence 396 CONCEPT 18.4 Many experiments show that species diversity is positively related to community function. 402 The Consequences of Diversity 402 A CASE STUDY REVISITED Powered by Prairies? Biodiversity and Biofuels 405 CONNECTIONS IN NATURE Barriers to Biofuels: The Plant Cell Wall Conundrum 406 UNIT 5 Ecosystems CHAPTER 19 Production 410 Life in the Deep Blue Sea, How Can It Be?: A Case Study 410 Introduction 411 CONCEPT 19.1 Energy in ecosystems originates with primary production by autotrophs. 412 Primary Production 412 ECOLOGICAL TOOLKIT 19.1 Remote Sensing 416 CONCEPT 19.2 Net primary production is constrained by both physical and biotic environmental factors. 418 Environmental Controls on NPP 418 CONCEPT 19.3 Global patterns of net primary production reflect climatic constraints and biome types. 423 Global Patterns of NPP 423

9 Contents xxi CONCEPT 19.4 Secondary production is generated through the consumption of organic matter by heterotrophs. 424 Secondary Production 424 A CASE STUDY REVISITED Life in the Deep Blue Sea, How Can It Be? 425 CONNECTIONS IN NATURE Energy-Driven Succession and Evolution in Hydrothermal Vent Communities 426 CHAPTER 20 Energy Flow and Food Webs 430 Toxins in Remote Places: A Case Study 430 Introduction 431 CONCEPT 20.1 Trophic levels describe the feeding positions of groups of organisms in ecosystems. 431 Feeding Relationships 431 CONCEPT 20.2 The amount of energy transferred from one trophic level to the next depends on food quality and consumer abundance and physiology. 433 Energy Flow among Trophic Levels 433 CONCEPT 20.3 Changes in the abundances of organisms at one trophic level can influence energy flow at multiple trophic levels. 438 Trophic Cascades 438 CONCEPT 20.4 Food webs are conceptual models of the trophic interactions of organisms in an ecosystem. 442 Food Webs 442 A CASE STUDY REVISITED Toxins in Remote Places 448 CONNECTIONS IN NATURE Biological Transport of Pollutants 449 CHAPTER 21 Nutrient Supply and Cycling 452 A Fragile Crust: A Case Study 452 Introduction 453 CONCEPT 21.1 Nutrients enter ecosystems through the chemical breakdown of minerals in rocks or through fixation of atmospheric gases. 454 Nutrient Requirements and Sources 454 CONCEPT 21.2 Chemical and biological transformations in ecosystems alter the chemical form and supply of nutrients. 458 Nutrient Transformations 458 CONCEPT 21.3 Nutrients cycle repeatedly through the components of ecosystems. 461 Nutrient Cycles and Losses 461 ECOLOGICAL TOOLKIT 21.1 Instrumenting Catchments 465 CONCEPT 21.4 Freshwater and marine ecosystems receive nutrient inputs from terrestrial ecosystems. 467 Nutrients in Aquatic Ecosystems 467 A CASE STUDY REVISITED A Fragile Crust 470 CONNECTIONS IN NATURE Nutrients, Disturbance, and Invasive Species 471 UNIT 6 Applied and Large-Scale Ecology CHAPTER 22 Conservation Biology 476 Can Birds and Bombs Coexist?: A Case Study 476 Introduction 477 CONCEPT 22.1 Conservation biology is an integrative discipline that applies the principles of ecology to the conservation of biodiversity. 477 Conservation Biology 477 CONCEPT 22.2 Biodiversity is declining globally. 480 Declining Biodiversity 480 CONCEPT 22.3 Primary threats to biodiversity include habitat loss, invasive species, overexploitation, pollution, disease, and climate change. 484 Threats to Biodiversity 484 CONCEPT 22.4 Conservation biologists use many tools and work at multiple scales to manage declining populations. 490 Approaches to Conservation 490 ECOLOGICAL TOOLKIT 22.1 Forensics in Conservation Biology 492

10 xxii Contents CONCEPT 22.5 Prioritizing species helps maximize the biodiversity that can be protected with limited resources. 495 Ranking Species for Protection 495 A CASE STUDY REVISITED Can Birds and Bombs Coexist? 497 CONNECTIONS IN NATURE Some Burning Questions 498 CHAPTER 23 Landscape Ecology and Ecosystem Management 501 Wolves in the Yellowstone Landscape: A Case Study 501 Introduction 502 ECOLOGICAL TOOLKIT 23.1 Geographic Information Systems (GIS) 503 CONCEPT 23.1 Landscape ecology examines spatial patterns and their relationship to ecological processes and changes. 504 Landscape Ecology 504 CONCEPT 23.2 Habitat loss and fragmentation decreases habitat area, isolates populations, and alters conditions at habitat edges. 508 Habitat Loss and Fragmentation 508 CONCEPT 23.3 Biodiversity can best be sustained by large reserves connected across the landscape and buffered from areas of intense human use. 514 Designing Nature Reserves 514 CONCEPT 23.4 Ecosystem management is a collaborative process with the maintenance of long-term ecological integrity as its core value. 518 Ecosystem Management 518 A CASE STUDY REVISITED Wolves in the Yellowstone Landscape 520 CONNECTIONS IN NATURE Future Changes in the Yellowstone Landscape 521 CHAPTER 24 Global Ecology 525 Dust Storms of Epic Proportions: A Case Study 525 Introduction 526 CONCEPT 24.1 Elements move among geologic, atmospheric, oceanic, and biological pools at a global scale. 526 Global Biogeochemical Cycles 526 CONCEPT 24.2 Earth is warming due to anthropogenic emissions of greenhouse gases. 532 Global Climate Change 532 CONCEPT 24.3 Anthropogenic emissions of sulfur and nitrogen cause acid deposition, alter soil chemistry, and affect the health of ecosystems. 539 Acid and Nitrogen Deposition 539 CONCEPT 24.4 Losses of ozone in the stratosphere and increases in ozone in the troposphere each pose risks to organisms. 543 Atmospheric Ozone 543 A CASE STUDY REVISITED Dust Storms of Epic Proportions 546 CONNECTIONS IN NATURE Dust as a Vector of Ecological Impacts 548 Appendix 551 Answers to Figure Legend and Review Questions 553 Glossary 575 Illustration Credits 587 Literature Cited 591 Index 613