Table Of ContentABOUT THE COVER
Average temperatures and precipitation change along mountain
slopes. In response to variation in physical conditions, the kinds
ecology of plants, animals, and microbes also change along altitudinal
gradients, with each species generally living within a restricted
range of conditions. Th is altitudinal variation in microclimate
McGraw-Hill ConnectPlus® interactive learning platform provides and biota is refl ected in the sweep of land in the southern Rocky
auto-graded assessments, a customizable, assignable eBook, and Mountains pictured on the cover, where lower altitudes radiate
powerful reporting—all in an easy-to-use interface. the vibrant colors of aspen trees in early autumn, while the high
By choosing ConnectPlus, instructors are providing snow-strewn peaks beyond jut against the deep blue northern sky
their students with a powerful tool for improving academic of approaching winter. Although the higher peaks may appear
performance and truly mastering course material. ConnectPlus devoid of vegetation from a distance, close inspection would show
allows students to practice important skills at their own pace that these higher zones support a diverse array of low-growing
and on their own schedule. Students’ assessment results and herbaceous plants. Strong physical gradients, such as this one,
instructor’s feedback are all saved online—so students can support high levels of biodiversity, as associations of organisms
continually review their progress and plot their course to success. change in response to diff ering physical conditions.
At this season, the aspen forests reveal another facet of
Go Green with ConnectPlus and connect your students biodiversity in this landscape. Genetic diversity within the aspen M
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with the tools and resources they’ll need to achieve success. population is signaled by diff erences in the timing of leaf color D
change. Th e cover shows one of the results of these genetic A
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according to diff ering schedules, as the trees transport nutrients 1
from leaves to their roots in response to autumn’s shorter days and 1
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decreasing temperatures. 1
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Studies of the relationships between organisms and the 5
environment make up the science we call ecology. Th is book was 1
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written to introduce this complex and fascinating discipline and /2
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to provide a conceptual foundation that will prepare the reader to /1
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look out onto a landscape, such as the one pictured on the cover, C
and see the broad outlines of the intricate connections weaving all Y
living beings and their environments on this planet into a vast web A
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Ecology
SIXTH EDITION
Concepts and Applications
Manuel C. Molles Jr.
University of New Mexico
Teresa Tibbets, Special Contributor
TM
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ECOLOGY: CONCEPTS AND APPLICATIONS, SIXTH EDITION
Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue
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ISBN 978-0-07-353249-3
MHID 0-07-353249-5
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Library of Congress Cataloging-in-Publication Data
Molles, Manuel C. (Manuel Carl), 1948-
Ecology : concepts and applications/Manuel C. Molles, Jr.—6th ed.
p. cm.
Includes index.
ISBN 978–0–07–353249–3—ISBN 0–07–353249–5 (hard copy : alk. paper) 1. Ecology. I. Title.
QH541.M553 2013
577—dc23 2011031001
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About the Author
Manuel C. Molles Jr.
is an emeritus Professor of Biology at the Uni-
versity of New Mexico, where he has been a member of the faculty and curator in the
Museum of Southwestern Biology since 1975 and where he continues to write and
conduct ecological research. He received his B.S. from Humboldt State University and
his Ph.D. from the Department of Ecology and Evolutionary Biology at the University
of Arizona. Seeking to broaden his geographic perspective, he has taught and conducted
ecological research in Latin America, the Caribbean, and Europe. He was awarded a
Fulbright Research Fellowship to conduct research on river ecology in Portugal and has
held visiting professor appointments in the Department of Zoology at the University
of Coimbra, Portugal, in the Laboratory of Hydrology at the Polytechnic University of
Madrid, Spain, and at the University of Montana’s Flathead Lake Biological Station.
Originally trained as a marine ecologist and fisheries biologist, the author has
worked mainly on river and riparian ecology at the University of New Mexico. His
research has covered a wide range of ecological levels, including behavioral ecology,
population biology, community ecology, ecosystem ecology, biogeography of stream
insects, and the influence of a large-scale climate system (El Niño) on the dynamics of
southwestern river and riparian ecosystems. His current research concerns the influence
of climate change and climatic variability on the dynamics of populations and commu-
nities along steep gradients of temperature and moisture in the mountains of the South-
west. Throughout his career, Dr. Molles has attempted to combine research, teaching,
and service, involving undergraduate as well as graduate students in his ongoing proj-
ects. At the University of New Mexico, he has taught a broad range of lower division,
upper division, and graduate courses, including Principles of Biology, Evolution and
Ecology, Stream Ecology, Limnology and Oceanography, Marine Biology, and Com-
munity and Ecosystem Ecology. He has taught courses in Global Change and River
Ecology at the University of Coimbra, Portugal, and General Ecology and Groundwater
and Riparian Ecology at the Flathead Lake Biological Station. Dr. Manuel Molles was
named Teacher of the Year by the University of New Mexico for 1995–1996 and Potter
Chair in Plant Ecology in 2000.
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Dedication
To Mary Anne
and
Misha
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Brief Contents
1 Introduction to Ecology: Historical Foundations and Developing Frontiers 1
Section Natural History and Evolution 11
I 2 Life on Land 11
3 Life in Water 45
4 Population Genetics and Natural Selection 77
Section Adaptations to the Environment 99
II
5 Temperature Relations 99
6 Water Relations 125
7 Energy and Nutrient Relations 149
8 Social Relations 173
Section P opulation Ecology 198
III
9 Population Distribution and Abundance 198
10 Population Dynamics 218
11 Population Growth 241
12 Life Histories 258
Section Interactions 282
IV
13 Competition 282
14 Exploitative Interactions: Predation, Herbivory, Parasitism, and Disease 303
15 Mutualism 329
Section Communities and Ecosystems 350
V
16 Species Abundance and Diversity 350
17 Species Interactions and Community Structure 370
18 Primary Production and Energy Flow 390
19 Nutrient Cycling and Retention 410
20 Succession and Stability 431
Section L arge-Scale Ecology 456
VI
21 Landscape Ecology 456
22 Geographic Ecology 481
23 Global Ecology 504
Appendix Statistical Tables 527
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Contents
3
Preface xiii Chapter Life in Water 45
1 Concepts 45
Chapter Introduction to Ecology: Historical
3.1 The Hydrologic Cycle 46
Foundations and Developing
Concept 3.1 Review 46
Frontiers 1
3.2 The Natural History of Aquatic Environments 46
Concepts 1 The Oceans 46
1.1 Overview of Ecology 2 Life in Shallow Marine Waters: Kelp Forests
Concept 1.1 Review 3 and Coral Gardens 51
Investigating the Evidence 3: Determining
1.2 Sampling Ecological Research 3
the Sample Median 52
The Ecology of Forest Birds: Old Tools and New 3
Marine Shores: Life between
F orest Canopy Research: A Physical and Scientific Frontier 6
High and Low Tides 55
Climatic and Ecological Change: Past and Future 6
Estuaries, Salt Marshes, and Mangrove
Concept 1.2 Review 8
Forests 58
Investigating the Evidence 1: The Scientific Method—
Rivers and Streams: Life Blood and Pulse
Questions and Hypotheses 9
of the Land 62
Lakes: Small Seas 66
I
Section Concept 3.2 Review 72
Applications: Biological Integrity—Assessing the Health
NATURAL HISTORY AND EVOLUTION
of Aquatic Systems 72
2 Number of Species and Species Composition 72
Chapter Life on Land 11
Trophic Composition 73
Concepts 11 Fish Abundance and Condition 73
Terrestrial Biomes 12 A Test 73
2.1 Large-Scale Patterns of Climatic Variation 13
4
Temperature, Atmospheric Circulation, Chapter Population Genetics and Natural
and Precipitation 13 Selection 77
Climate Diagrams 15
Concepts 77
Concept 2.1 Review 16
4.1 Variation Within Populations 79
2.2 Soil: The Foundation of Terrestrial Biomes 16
Variation in a Widely Distributed Plant 79
Investigating the Evidence 2: Determining
the Sample Mean 18 Variation in Alpine Fish Populations 80
Concept 2.2 Review 19 Concept 4.1 Review 82
2.3 Natural History and Geography of Biomes 19 4.2 Hardy-Weinberg 83
Tropical Rain Forest 19 Calculating Gene Frequencies 83
Tropical Dry Forest 21 Concept 4.2 Review 85
Tropical Savanna 23 4.3 The Process of Natural Selection 85
Desert 25 Stabilizing Selection 85
Mediterranean Woodland and Shrubland 27 Directional Selection 85
Temperate Grassland 30 Disruptive Selection 86
Temperate Forest 31 Concept 4.3 Review 87
Boreal Forest 34 4.4 Evolution by Natural Selection 87
Tundra 35
Heritability: Essential for Evolution 87
Mountains: Islands in the Sky 38
Investigating the Evidence 4: Variation in Data 88
Concept 2.3 Review 41
Directional Selection: Rapid Adaptation by Soapberry Bugs
Applications: Climatic Variation and the Palmer Drought to New Host Plants 89
Severity Index 41 Concept 4.4 Review 92
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Contents vii
4.5 Change Due to Chance 92 Water Movement Between Soils and Plants 129
Evidence of Genetic Drift in Chihuahua Spruce 92 Concept 6.1 Review 131
Genetic Variation in Island Populations 93 6.2 Water Regulation on Land 131
Genetic Diversity and Butterfly Extinctions 94 Water Acquisition by Animals 131
Concept 4.5 Review 95 Water Acquisition by Plants 133
Applications: Evolution and Agriculture 95 Water Conservation by Plants and Animals 134
Evolution of Herbicide Resistance in Weeds 95 Investigating the Evidence 6: Sample Size 136
Dissimilar Organisms with Similar Approaches
to Desert Life 138
II
Two Arthropods with Opposite Approaches
Section
to Desert Life 139
ADAPTATIONS TO THE ENVIRONMENT Concept 6.2 Review 142
6.3 Water and Salt Balance in Aquatic
5
Chapter Temperature Relations 99 Environments 142
Marine Fish and Invertebrates 142
Concepts 99
Freshwater Fish and Invertebrates 143
5.1 Microclimates 100 Concept 6.3 Review 144
Altitude 100
Applications: Using Stable Isotopes to Study Water Uptake
Aspect 101
by Plants 144
Vegetation 101
Stable Isotope Analysis 145
Color of the Ground 101
Using Stable Isotopes to Identify Plant Water Sources 146
Presence of Boulders and Burrows 102
Aquatic Temperatures 102 7
Chapter Energy and Nutrient Relations 149
Concept 5.1 Review 103
5.2 Evolutionary Trade-Offs 103 Concepts 149
The Principle of Allocation 103 7.1 Photosynthetic Autotrophs 151
Concept 5.2 Review 104 The Solar-Powered Biosphere 151
5.3 T emperature and Performance of Organisms 104 Concept 7.1 Review 155
Investigating the Evidence 5: Laboratory 7.2 Chemosynthetic Autotrophs 155
Experiments 106 Concept 7.2 Review 155
Extreme Temperatures and Photosynthesis 106 7.3 H eterotrophs 155
Temperature and Microbial Activity 107 Chemical Composition and Nutrient Requirements 155
Concept 5.3 Review 109 Concept 7.3 Review 162
5.4 Regulating Body Temperature 109 7.4 Energy Limitation 162
Balancing Heat Gain against Heat Loss 109 Photon Flux and Photosynthetic Response Curves 163
Temperature Regulation by Plants 110 Food Density and Animal Functional Response 164
Temperature Regulation by Ectothermic Animals 112 Concept 7.4 Review 165
Temperature Regulation by Endothermic Animals 113
7.5 Optimal Foraging Theory 165
Temperature Regulation by Thermogenic Plants 117
Testing Optimal Foraging Theory 165
Concept 5.4 Review 119
Optimal Foraging by Plants 166
5.5 S urviving Extreme Temperatures 119 Investigating the Evidence 7: Scatter Plots and the
Inactivity 119 Relationship between Variables 168
Reducing Metabolic Rate 120 Concept 7.5 Review 169
Hibernation by a Tropical Species 121 Applications: Bioremediation—Using the Trophic Diversity
Concept 5.5 Review 121 of Bacteria to Solve Environmental Problems 169
Applications: Local Extinction of a Land Snail in an Urban Leaking Underground Storage Tanks 169
Heat Island 121 Cyanide and Nitrates in Mine Spoils 169
6 8
Chapter Water Relations 125 Chapter Social Relations 173
Concepts 125 Concepts 173
6.1 Water Availability 126 8.1 Mate Choice versus Predation 175
Water Content of Air 127 Mate Choice and Sexual Selection in Guppies 176
Water Movement in Aquatic Environments 128 Concept 8.1 Review 178
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viii Contents
10
8.2 Mate Choice and Resource Provisioning 179 Chapter Population Dynamics 218
Concept 8.2 Review 182
Concepts 218
8.3 Nonrandom Mating in a Plant Population 182
10.1 Dispersal 219
Concept 8.3 Review 184
Dispersal of Expanding Populations 220
8.4 Sociality 184 Range Changes in Response to Climate Change 221
Cooperative Breeders 184 Dispersal in Response to Changing Food Supply 222
Investigating the Evidence 8: Estimating Heritability Using Dispersal in Rivers and Streams 223
Regression Analysis 188 Concept 10.1 Review 224
Concept 8.4 Review 191
10.2 Metapopulations 224
8.5 Eusociality 191
A Metapopulation of an Alpine Butterfly 224
Eusocial Species 191 Dispersal within a Metapopulation
Evolution of Eusociality 193 of Lesser Kestrels 225
Concept 8.5 Review 195 Concept 10.2 Review 226
Applications: Behavioral Ecology 10.3 Patterns of Survival 226
and Conservation 195
Estimating Patterns of Survival 226
Tinbergen’s Framework 195 High Survival among the Young 227
Environmental Enrichment and Development Constant Rates of Survival 229
of Behavior 195 High Mortality among the Young 229
Three Types of Survivorship Curves 230
Concept 10.3 Review 230
III
Section 10.4 Age Distribution 230
Contrasting Tree Populations 230
POPULATION ECOLOGY
A Dynamic Population in a Variable Climate 231
9 Concept 10.4 Review 232
Chapter Population Distribution
10.5 Rates of Population Change 232
and Abundance 198
Estimating Rates for an Annual Plant 232
Concepts 198 Estimating Rates When Generations Overlap 234
Concept 10.5 Review 235
9.1 Distribution Limits 200
Investigating the Evidence 10: Hypotheses and Statistical
Kangaroo Distributions and Climate 200
Significance 236
A Tiger Beetle of Cold Climates 201
Applications: Using Population Dynamics to Assess the
Distributions of Plants along a Moisture-Temperature
Impact of Pollutants 236
Gradient 202
Distributions of Barnacles along an Intertidal Exposure
Gradient 203 11
Chapter Population Growth 241
Concept 9.1 Review 204
Concepts 241
9.2 Patterns on Small Scales 204
Scale, Distributions, and Mechanisms 205 11.1 Geometric and Exponential Population Growth 242
Distributions of Tropical Bee Colonies 205 Geometric Growth 242
Distributions of Desert Shrubs 206 Exponential Growth 243
Concept 9.2 Review 208 Exponential Growth in Nature 244
Concept 11.1 Review 245
9.3 Patterns on Large Scales 208
Bird Populations across North America 208 11.2 Logistic Population Growth 245
Investigating the Evidence 9: Clumped, Random, Concept 11.2 Review 248
and Regular Distributions 209 11.3 Limits to Population Growth 248
Plant Distributions along Moisture Gradients 210
Environment and Birth and Death among Darwin’s
Concept 9.3 Review 211 Finches 248
9.4 Organism Size and Population Density 212 Investigating the Evidence 11: Frequency of Alternative
Animal Size and Population Density 212 Phenotypes in a Population 250
Plant Size and Population Density 212 Concept 11.3 Review 252
Concept 9.4 Review 213 Applications: The Human Population 252
Applications: Rarity and Vulnerability Distribution and Abundance 253
to Extinction 213 Population Dynamics 254
Seven Forms of Rarity and One of Abundance 214 Population Growth 255
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Contents ix
12
Chapter Life Histories 258 Applications: Competition between
Native and Invasive Species 300
Concepts 258
12.1 Offspring Number versus Size 259 14
Chapter Exploitative Interactions: Predation,
Egg Size and Number in Fish 260
Herbivory, Parasitism, and
Seed Size and Number in Plants 261
Disease 303
Seed Size and Seedling Performance 263
Concept 12.1 Review 265
Concepts 303
12.2 Adult Survival and Reproductive Allocation 266
14.1 Complex Interactions 304
Life History Variation among Species 266
Parasites and Pathogens that Manipulate Host
Life History Variation within Species 267
Behavior 304
Concept 12.2 Review 270
The Entangling of Exploitation with Competition 306
12.3 Life History Classification 270 Concept 14.1 Review 308
r and K Selection 270 14.2 Exploitation and Abundance 308
Plant Life Histories 271
A Herbivorous Stream Insect and Its Algal Food 308
Investigating the Evidence 12: A Statistical Test
Bats, Birds, and Herbivory in a Tropical Forest 309
for Distribution Pattern 272
A Pathogenic Parasite, a Predator, and Its Prey 311
Opportunistic, Equilibrium, and Periodic Life
Concept 14.2 Review 312
Histories 274
14.3 Dynamics 312
Lifetime Reproductive Effort and Relative Offspring Size:
Two Central Variables? 275 Cycles of Abundance in Snowshoe Hares
and Their Predators 312
Concept 12.3 Review 276
Investigating the Evidence 14: Standard Error
Applications: Using Life History Information to Restore
of the Mean 314
Riparian Forests 277
Experimental Test of Food and Predation Impacts 316
IV Population Cycles in Mathematical
Section and Laboratory Models 316
Concept 14.3 Review 319
INTERACTIONS
14.4 Refuges 319
13 Refuges and Host Persistence in Laboratory
Chapter Competition 282
and Mathematical Models 319
Concepts 282 Exploited Organisms and Their Wide Variety of “Refuges” 321
Concept 14.4 Review 325
13.1 Intraspecific Competition 284
Intraspecific Competition among Plants 284 Applications: The Value of Pest Control by Bats:
A Case Study 325
Intraspecific Competition among Planthoppers 285
Interference Competition among
15
Terrestrial Isopods 285 Chapter Mutualism 329
Concept 13.1 Review 286
Concepts 329
13.2 Competitive Exclusion and Niches 286
15.1 Plant Mutualisms 330
The Feeding Niches of Darwin’s Finches 286
The Habitat Niche of a Salt Marsh Grass 287 Plant Performance and Mycorrhizal Fungi 330
Concept 13.2 Review 288 Ants and Swollen Thorn Acacias 334
A Temperate Plant Protection Mutualism 337
13.3 Mathematical and Laboratory Models 289
Concept 15.1 Review 339
Modeling Interspecific Competition 289
15.2 C oral Mutualisms 340
Laboratory Models of Competition 291
Concept 13.3 Review 292 Zooxanthellae and Corals 340
A Coral Protection Mutualism 340
13.4 Competition and Niches 292
Concept 15.2 Review 342
Niches and Competition Among Plants 292
15.3 Evolution of Mutualism 342
Niche Overlap and Competition between Barnacles 293
Competition and the Habitat of a Salt Marsh Grass 294 Investigating the Evidence 15: Confidence
Intervals 343
Competition and the Niches of Small Rodents 294
Facultative Ant-Plant Protection Mutualisms 345
Character Displacement 296
Concept 15.3 Review 345
Evidence for Competition in Nature 298
Investigating the Evidence 13: Field Experiments 299 Applications: Mutualism and Humans 345
Concept 13.4 Review 300 Guiding Behavior 346
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