Table Of ContentESSENTIALS
OF ECOLOGY
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ESSENTIALS
OF ECOLOGY
Third Edition
Colin R. Townsend
Department of Zoology, University of Otago, Dunedin, New Zealand
Michael Begon
Population Biology Research Group, School of Biological Sciences
The University of Liverpool, Liverpool, UK
John L. Harper
Professor Emeritus in the University of Wales
Visiting Professor in the University of Exeter, Exeter, UK
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© 2008 by Blackwell Publishing
BLACKWELL PUBLISHING
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First edition published 2000 by Blackwell Publishing
Second edition published 2003
Third edition published 2008
1
2008
Library of Congress Cataloging-in-Publication Data
Townsend, Colin R.
Essentials of ecology / Colin R. Townsend, Michael Begon, John L. Harper.—3rd ed.
p.
cm.
Includes bibliographical references and index.
ISBN 978-1-4051-5658-5 (pbk. : alk. paper)
1. Ecology.
I. Begon, Michael.
II. Harper, John L.
III. Title.
QH541.T66 2008
577—dc22
2007034694
A catalogue record for this title is available from the British Library.
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v
Full contents vi
Preface x
Acknowledgments xii
Part I Introduction 1
1
Ecology and how to do it 3
2
Ecology’s evolutionary backdrop 36
Part II Conditions and Resources 67
3
Physical conditions and the availability of resources 69
4
Conditions, resources and the world’s communities 110
Part III Individuals, Populations, Communities and Ecosystems 143
5
Birth, death and movement 145
6
Interspecific competition 182
7
Predation, grazing and disease 217
8
Evolutionary ecology 251
9
From populations to communities 281
10
Patterns in species richness 323
11
The flux of energy and matter through ecosystems 357
Part IV Applied Issues in Ecology 387
12
Sustainability 389
13
Habitat degradation 423
14
Conservation 455
References 483
Index 495
SHORT CONTENTS
Short contents
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CONTENTS
Preface x
Acknowledgments xii
Part I Introduction 1
1
Ecology and how to do it 3
1.1
Introduction 4
1.2
Scales, diversity and rigor 7
1.3
Ecology in practice 17
2
Ecology’s evolutionary backdrop 36
2.1
Introduction 37
2.2
Evolution by natural selection 37
2.3
Evolution within species 41
2.4
The ecology of speciation 51
2.5
Effects of climatic change on the evolution and distribution of species 58
2.6
Effects of continental drift on the ecology of evolution 60
2.7
Interpreting the results of evolution: convergents and parallels 63
Part II Conditions and Resources 67
3
Physical conditions and the availability
of resources 69
3.1
Introduction 70
3.2
Environmental conditions 71
3.3
Plant resources 84
3.4
Animals and their resources 95
3.5
Effects of intraspecific competition for resources 103
3.6
Conditions, resources and the ecological niche 106
vi
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4
Conditions, resources and the world’s
communities 110
4.1
Introduction 111
4.2
Geographic patterns at large and small scales 111
4.3
Temporal patterns in conditions and resources 117
4.4
Terrestrial biomes 119
4.5
Aquatic environments 130
Part III Individuals, Populations,
Communities and Ecosystems 143
5
Birth, death and movement 145
5.1
Introduction 146
5.2
Life cycles 151
5.3
Monitoring birth and death: life tables and fecundity schedules 156
5.4
Dispersal and migration 164
5.5
The impact of intraspecific competition on populations 169
5.6
Life history patterns 175
6
Interspecific competition 182
6.1
Introduction 183
6.2
Ecological effects of interspecific competition 183
6.3
Evolutionary effects of interspecific competition 197
6.4
Interspecific competition and community structure 200
6.5
How significant is interspecific competition in practice? 208
7
Predation, grazing and disease 217
7.1
Introduction 218
7.2
Prey fitness and abundance 220
7.3
The subtleties of predation 222
7.4
Predator behavior: foraging and transmission 228
7.5
Population dynamics of predation 233
7.6
Predation and community structure 246
8
Evolutionary ecology 251
8.1
Introduction 252
8.2
Molecular ecology: differentiation within and between species 253
8.3
Coevolutionary arms races 262
8.4
Mutualistic interactions 267
Contents
vii
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9 From populations to communities 281
9.1
Introduction 282
9.2
Multiple determinants of the dynamics of populations 283
9.3
Dispersal, patches and metapopulation dynamics 294
9.4
Temporal patterns in community composition 299
9.5
Food webs 307
10 Patterns in species richness 323
10.1 Introduction 324
10.2 A simple model of species richness 326
10.3 Spatially varying factors that influence species richness 328
10.4 Temporally varying factors that influence species richness 337
10.5 Gradients of species richness 340
10.6 Patterns in taxon richness in the fossil record 349
10.7 Appraisal of patterns in species richness 352
11 The flux of energy and matter through ecosystems 357
11.1 Introduction 358
11.2 Primary productivity 360
11.3 The fate of primary productivity 364
11.4 The process of decomposition 369
11.5 The flux of matter through ecosystems 374
11.6 Global biogeochemical cycles 380
Part IV Applied Issues in Ecology 387
12 Sustainability 389
12.1 Introduction 390
12.2 The human population ‘problem’ 391
12.3 Harvesting living resources from the wild 399
12.4 The farming of monocultures 405
12.5 Pest control 412
12.6 Integrated farming systems 417
12.7 Forecasting agriculturally driven global environmental change 419
13 Habitat degradation 423
13.1 Introduction 424
13.2 Degradation via cultivation 428
13.3 Power generation and its diverse effects 435
13.4 Degradation in urban and industrial landscapes 442
13.5 Maintenance and restoration of ecosystem services 448
Contents
viii
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14 Conservation 455
14.1 Introduction 456
14.2 Threats to biodiversity 459
14.3 Conservation in practice 468
14.4 Conservation in a changing world 476
14.5 Finale 479
References 483
Index 495
Contents
ix
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B
y writing this book we hope to share with you some of our wonder at the
complexity of nature, but we must all also be aware that there is a darker
side: the fear that we are destroying our natural environments and the services
they provide. All of us need to be ecologically literate so that we can take part
in political debate and contribute to solving the ecological problems that we
carry with us into the new millennium. We hope our book will contribute to this
objective.
The genesis of this book can be found in the more comprehensive treatment of
ecology in our big book Ecology: from Individuals to Ecosystems (Begon, Townsend
& Harper, 4th edn, 2006). This is used as an advanced university text around
the world, but many of our colleagues have called for a more succinct treatment
of the essence of the subject. Thus, we were spurred into action to produce a
distinctively different book, written with clear objectives for a different audience
– those taking a semester-long beginners course in the essentials of ecology. We
hope that at least some readers will be excited enough to go on to sample the big
book and the rich literature of ecology that it can lead into.
In this third edition of Essentials of Ecology we have made the text, including
mathematical topics, even more accessible. Ecology is a vibrant subject and this
is reflected by our inclusion of literally hundreds of new studies. Some readers will
be engaged most by the fundamental principles of how ecological systems work.
Others will be impatient to focus on the ecological problems caused by human
activities. We place heavy emphasis on both fundamental and applied aspects of
ecology: there is no clear boundary between the two. However, we have chosen to
deal first in a systematic way with the fundamental side of the subject, and we have
done this for a particular reason. An understanding of the scope of the problems
facing us (the unsustainable use of ecological resources, pollution, extinctions
and the erosion of natural biodiversity) and the means to counter and solve these
problems depend absolutely on a proper grasp of ecological fundamentals.
The book is divided into four sections. In the introduction we deal with two
foundations for the subject that are often neglected in texts. Chapter 1 aims to
show not only what ecology is but also how ecologists do it – how ecological
understanding is achieved, what we understand (and, just as important, what we
do not yet understand) and how our understanding helps us predict and manage.
We then introduce ‘Ecology’s evolutionary backdrop’ and show that ecologists
need a full understanding of the evolutionary biologist’s discipline in order to
make sense of patterns and processes in nature (Chapter 2).
What makes an environment habitable for particular species is that they can
tolerate the physicochemical conditions there and find in it their essential resources.
PREFACE
Preface
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In the second section we deal with conditions and resources, both as they influence
individual species (Chapter 3) and in terms of their consequences for the com-
position and distribution of multispecies communities, for example in deserts,
rain forests, rivers, lakes and oceans (Chapter 4).
The third section (Chapters 5–11) deals systematically with the ecology of
individual organisms, populations of a single species, communities consisting of
many populations, and ecosystems (where we focus on the fluxes of energy and
matter between and within communities). To understand patterns and processes at
each of these levels we need to know the behavior of the level below. This section
also includes a new Chapter 8 on ‘Evolutionary ecology’, responding to the feelings
of some readers that, although evolutionary ideas pervade the book, there was still
not sufficient evolution for a book at this level.
Finally, armed with knowledge and understanding of the fundamentals, the
book turns to the applied questions of how to deal with pests and manage resources
sustainably (whether wild populations of fish or agricultural monocultures)
(Chapter 12), then to a diversity of pollution problems ranging from local enrich-
ment of a lake by sewage to global climate change associated with the use of
fossil fuels (Chapter 13) and lastly we develop an armory of approaches that
may help us to save endangered species from extinction and conserve some of
the biodiversity of nature for our descendants (Chapter 14).
A number of pedagogical features have been included to help you.
l Each chapter begins with a set of key concepts that you should understand
before proceeding to the next chapter.
l Marginal headings provide signposts of where you are on your journey
through each chapter – these will also be useful revision aids.
l Each chapter concludes with a summary and a set of review questions, some
of which are designated challenge questions.
l You will also find three categories of boxed text:
l ‘Historical landmarks’ boxes emphasize some landmarks in the
development of ecology.
l ‘Quantitative aspects’ boxes set aside mathematical and quantitative
aspects of ecology so they do not unduly interfere with the flow of the
text and so you can consider them at leisure.
l ‘Topical ECOncerns’ boxes highlight some of the applied problems in
ecology, particularly those where there is a social or political dimension
(as there often is). In these, you will be challenged to consider some
ethical questions related to the knowledge you are gaining.
An important further feature of the book is the companion internet web
site, e.cology, accessed through www.blackwellpublishing.com and linked to the
companion site of our big book, Ecology. This provides an easy-to-use range of
resources to aid study and enhance the content of the book. Features include
self-assessment multiple choice questions for each chapter in the book, an inter-
active tutorial to help students to understand the use of mathematical modeling
in ecology, and high-quality images of the figures in the book that teachers can
use in preparing their lectures or lessons.
Preface
xi
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I
t is a pleasure to record our gratitude to the people who helped with the
planning and writing of this book. Going back to the first edition, we thank Bob
Campbell and Simon Rallison for getting the original enterprise off the ground
and Nancy Whilton and Irene Herlihy for ably managing the project; and for the
second edition, Nathan Brown (Blackwell, US) and Rosie Hayden (Blackwell, UK)
for making it so easy for us to take this book from manuscript into print. For this
third edition, we especially thank Nancy Whilton and Elizabeth Frank in Boston
for persuading us to pick up our pens again (not literally) and Rosie Hayden, again,
and Jane Andrew and Ward Cooper for seeing us through production. We are
also grateful to the following colleagues who provided insightful reviews of early
drafts of one or more chapters. For the first edition, Tim Mousseau (University
of South Carolina), Vickie Backus (Middlebury College), Kevin Dixon (Arizona
State University, West), James Maki (Marquette University), George Middendorf
(Howard University), William Ambrose (Bates College), Don Hall (Michigan
State University), Clayton Penniman (Central Connecticut State University), David
Tonkyn (Clemson University), Sara Lindsay (Scripps Institute of Oceanography),
Saran Twombly (University of Rhode Island), Katie O’Reilly (University of
Portland), Catherine Toft (UC Davis), Bruce Grant (Widener University), Mark
Davis (Macalester College), Paul Mitchell (Staffordshire University, UK) and
William Kirk (Keele University, UK); and for the second, James Cahill (University
of Alberta), Liane Cochrane-Stafira (Saint Xavier University), Hans deKroon
(University of Nijmegen), Jake Weltzin (University of Tennessee at Knoxville)
and Alan Wilmot (University of Derby, UK).
For this edition, our long-time mentor and collaborator John Harper has stepped
from the treadmill to more fully enjoy his retirement. We owe him a special debt
of gratitude that extends far beyond the past co-authorship of this book into all
aspects of our lives as ecologists.
Last, and perhaps most, we are glad to thank our wives and families for con-
tinuing to support us, listen to us, and ignore us, precisely as required – thanks to
Laurel, Dominic, Jenny, Brennan and Amelie, and to Linda, Jessi and Rob.
The publisher would like to thank Denis Saunders, from CSIRO, for use of the
image in part 4 of the book.
ACKNOWLEDGMENTS
Acknowledgments
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PART ONE
Introduction
1 | Ecology and how to do it 3
2 | Ecology’s evolutionary backdrop 36
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