Tropical Forest Community Ecology E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 1350

Veröffentlichungsjahr: 2011

Beschreibung

Historically, tropical ecology has been a science often content with descriptive and demographic approaches, which is understandable given the difficulty of studying these ecosystems and the need for basic demographic information. Nonetheless, over the last several years, tropical ecologists have begun to test more sophisticated ecological theory and are now beginning to address a broad array of questions that are of particular importance to tropical systems, and ecology in general. Why are there are so many species in tropical forests and what mechanisms are responsible for the maintenance of that vast species diversity? What factors control species coexistence? Are there common patterns of species abundance and distribution across broad geographic scales? What is the role of trophic interactions in these complex ecosystems? How can these fragile ecosystems be conserved?

Containing contributions from some of the world’s leading tropical ecologists, Tropical Forest Community Ecology provides a summary of the key issues in the discipline of tropical ecology:

• Includes contributions from some of the world’s leading tropical ecologists
  
• Covers patterns of species distribution, the maintenance of species diversity, the community ecology of tropical animals, forest regeneration and conservation of tropical ecosystems

Leseprobe

Contents

PREFACE

FOREWORD

LIST OF CONTRIBUTORS

Section 1 INTRODUCTION

Chapter 1 SCOPE OF THE BOOK AND KEY CONTRIBUTIONS

LARGE-SCALE PATTERNS IN TROPICAL COMMUNITIES

TESTING THEORIES OF FOREST REGENERATION AND THE MAINTENANCE OF SPECIES DIVERSITY

ANIMAL COMMUNITY ECOLOGY AND TROPHIC INTERACTIONS

SECONDARY FOREST SUCCESSION, DYNAMICS, AND INVASION

TROPICAL FOREST CONSERVATION

REFERENCES

Section 2 LARGE-SCALE PATTERNS IN TROPICAL COMMUNITIES

Chapter 2 SPATIAL VARIATION IN TREE SPECIES COMPOSITION ACROSS TROPICAL FORESTS: PATTERN AND PROCESS

OVERVIEW

INTRODUCTION

DOCUMENTING PATTERNS OF SPATIAL VARIATION IN SPECIES DIVERSITY

SEARCHING FOR ENVIRONMENTAL CORRELATES OF SPATIAL VARIATION IN DIVERSITY

UNDERSTANDING THE CAUSES OF SPATIAL VARIATION IN SPECIES DIVERSITY

TESTING THEORIES

DISCUSSION

ACKNOWLEDGMENTS

REFERENCES

Chapter 3 THE DISPARITY IN TREE SPECIES RICHNESS AMONG TROPICAL, TEMPERATE, AND BOREAL BIOMES: THE GEOGRAPHIC AREA AND AGE HYPOTHESIS

OVERVIEW

INTRODUCTION

MECHANISMS

TESTING THE GAH

TESTING THE GAAH

ESTIMATING HISTORIES OF BIOME AREAS

EMPIRICAL TESTS OF THE GAH AND GAAH

DISCUSSION

CONCLUSION

ACKNOWLEDGMENTS

REFERENCES

Chapter 4 EXPLAINING GEOGRAPHIC RANGE SIZE BY SPECIES AGE: A TEST USING NEOTROPICAL PIPER SPECIES

OVERVIEW

INTRODUCTION

EMPIRICAL TESTS OF AGE AND AREA

AN EMPIRICAL TEST USING A TROPICAL PLANT GENUS

WHAT DO OTHER TROPICAL PLANT CLADES TELL US?

AN AGE-AND-AREA HYPOTHESIS FOR MODERN TIMES

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

APPENDIX

Chapter 5 PATTERNS OF HERBIVORY AND DEFENSE IN TROPICAL DRY AND RAIN FORESTS

OVERVIEW

INTRODUCTION

THEORETICAL FRAMEWORKS AND PREDICTIONS

THE INFORMATION BASE TO TEST THE PREDICTIONS

DOES EMPIRICAL EVIDENCE MATCH PREDICTIONS?

PHYLOGENETIC INERTIA

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 6 ECOLOGICAL ORGANIZATION, BIOGEOGRAPHY, AND THE PHYLOGENETIC STRUCTURE OF TROPICAL FOREST TREE COMMUNITIES

OVERVIEW

ECOLOGICAL ORGANIZATION OF TROPICAL TREE COMMUNITIES

EVOLUTION OF ECOLOGICAL CHARACTERS IN TROPICAL FOREST TREES

THE PHYLOGENETIC STRUCTURE OF SPECIES ASSEMBLAGES

TOWARDS PREDICTING TROPICAL CLADE COMPOSITION

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 7 LARGE TROPICAL FOREST DYNAMICS PLOTS: TESTING EXPLANATIONS FOR THE MAINTENANCE OF SPECIES DIVERSITY

OVERVIEW

INTRODUCTION

ECOLOGICAL EXPLANATIONS FOR SPECIES DIVERSITY

DEVELOPMENT OF THE CTFS NETWORK OF LARGE FDPS

LARGE FDPS AND ECOLOGICAL THEORY

LIMITATIONS

FUTURE RESEARCH IN FDPS

ACKNOWLEDGMENTS

REFERENCES

Section 3 TESTINGTHEORIES OF FOREST REGENERATION AND THE MAINTENANCE OF SPECIES DIVERSITY

Chapter 8 TROPICAL FOREST ECOLOGY: STERILE OR VIRGIN FOR THEORETICIANS?

OVERVIEW

THE QUESTIONS: WHAT MUST WE UNDERSTAND ABOUT TROPICAL FORESTS?

FRAMING A MATHEMATICAL THEORY OF FOREST ECOLOGY

WHAT MATHEMATICAL THEORY HAS DONE

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 9 APPROACHING ECOLOGICAL COMPLEXITY FROM THE PERSPECTIVE OF SYMMETRIC NEUTRAL THEORY

OVERVIEW

INTRODUCTION

THEORETICAL RECIPE: START SIMPLY, ADD AS FEW FREE PARAMETERS AS POSSIBLE, STIR VIGOROUSLY

NEXT STEP: ADD A BIT MORE COMPLEXITY – LOCAL COMMUNITIES AND DISPERSAL LIMITATION

NOW, ADD YET MORE COMPLEXITY: SYMMETRIC DENSITY-AND FREQUENCY DEPENDENCE

CONFRONTING THE THEORY WITH RELATIVE ABUNDANCE DATA ON TROPICAL TREE COMMUNITIES

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 10 FUNCTIONAL BASIS FOR RESOURCE NICHE PARTITIONING BY TROPICAL TREES

OVERVIEW

NICHE – DEFINITIONS AND IMPLICATIONS

FUNCTIONAL MECHANISM FOR LIGHT COMPETITION

TRADE-OFFS PROMOTING SPECIES RICHNESS WITHIN A HORIZONTAL PLANE

VERTICAL LIGHT GRADIENTS AND ONTOGENETIC SHIFTS

NICHE HYPERSPACE

CONCLUDING REMARKS

ACKNOWLEDGMENTS

REFERENCES

Chapter 11 COLONIZATION-RELATED TRADE-OFFS IN TROPICAL FORESTS AND THEIR ROLE IN THE MAINTENANCE OF PLANT SPECIES DIVERSITY

OVERVIEW

INTRODUCTION

THEORY ON COLONIZATION-RELATED TRADE-OFFS AND DIVERSITY MAINTENANCE

COLONIZATION-RELATED TRADE-OFFS AND HABITAT PARTITIONING

METHODS FOR EVALUATING THE PRESENCE AND ROLE OF COLONIZATION-RELATED TRADE-OFFS

EMPIRICAL EVIDENCE IN TROPICAL FORESTS

CONCLUSIONS AND FUTURE DIRECTIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 12 TREEFALL GAPS AND THE MAINTENANCE OF PLANT SPECIES DIVERSITY IN TROPICAL FORESTS

OVERVIEW

INTRODUCTION

PROCESSES AND PATHWAYS OF GAP-PHASE REGENERATION

HYPOTHESES AND MECHANISMS BY WHICH TREEFALL GAPS ARE PROPOSED TO MAINTAIN DIVERSITY

EMPIRICAL TESTS: IS THERE EVIDENCE TO SUPPORT THE GAP HYPOTHESIS?

VARIATION IN THE IMPACT OF GAPS ACROSS BROAD ENVIRONMENTAL GRADIENTS

TREEFALL GAPS PROVIDE A POOR MODEL TO TEST THE INTERMEDIATE DISTURBANCE HYPOTHESIS

CONCLUSIONS

REFERENCES

Chapter 13 CHALLENGES ASSOCIATED WITH TESTING AND FALSIFYING THE JANZEN–CONNELL HYPOTHESIS: A REVIEW AND CRITIQUE

OVERVIEW

INTRODUCTION

A REVIEW OF STUDIES TESTING FOR JANZEN–CONNELL EFFECTS

CHALLENGES AND ISSUES ASSOCIATED WITH TESTING, EVALUATING, AND FALSIFYING THE JANZEN–CONNELL HYPOTHESIS

ACKNOWLEDGMENTS

REFERENCES

Chapter 14 SEED LIMITATION AND THE COEXISTENCE OF PIONEER TREE SPECIES

OVERVIEW

INTRODUCTION

ARE TROPICAL PIONEERS SEED LIMITED?

DO PIONEER RECRUITMENT PATTERNS REFLECT SEED LIMITATION?

SEED LIMITATION IN CONTEXT

CONCLUSIONS

REFERENCES

Chapter 15 ENDOPHYTIC FUNGI: HIDDEN COMPONENTS OF TROPICAL COMMUNITY ECOLOGY

OVERVIEW

INTRODUCTION

ENDOPHYTE TRANSMISSION IN TROPICAL FORESTS

ENDOPHYTE COLONIZATION AND ABUNDANCE IN TROPICAL LEAVES

TROPICAL ENDOPHYTE DIVERSITY

BEYOND ALPHA-DIVERSITY: HOST AFFINITY AND SPATIAL STRUCTURE

FUNGAL ENDOPHYTES AND TROPICAL FOREST COMMUNITY ECOLOGY

ENDOPHYTES AS NEUTRAL INHABITANTS OF THEIR HOSTS

ENDOPHYTES AS PARASITES

ENDOPHYTES AS MUTUALISTS

DO ENDOPHYTES ACT AS ENVIRONMENTALLY ACQUIRED IMMUNE SYSTEMS?

SANTA ROSALIA’S FUNGAL BLESSINGS

ACKNOWLEDGMENTS

REFERENCES

Section 4 ANIMAL COMMUNITY ECOLOGY AND TROPHIC INTERACTIONS

Chapter 16 TROPICAL TRITROPHIC INTERACTIONS: NASTY HOSTS AND UBIQUITOUS CASCADES

OVERVIEW

INTRODUCTION

TOUGHER PREDATORS, NASTIER PLANTS, MORE SPECIALIZED CONSUMERS?

EVOLUTION OF DIETARY SPECIALIZATION

TROPHIC CASCADES

FUTURE DIRECTIONS

CONCLUSION

ACKNOWLEDGMENTS

REFERENCES

Chapter 17 VARIATION IN TREE SEEDLING AND ARBUSCULAR MYCORRHIZAL FUNGAL SPORE RESPONSES TO THE EXCLUSION OF TERRESTRIAL VERTEBRATES: IMPLICATIONS FOR HOW VERTEBRATES STRUCTURE TROPICAL COMMUNITIES

OVERVIEW

INTRODUCTION

COMPARATIVE ATTRIBUTES OF AUSTRALIAN RAINFORESTS

RESULTS OF TERRESTRIAL VERTEBRATE EXCLUSION FROM AN AUSTRALIAN RAINFOREST

POTENTIAL REASONS FOR THE DIFFERENT RESPONSE OF SEEDLINGS AND AMF SPORES

IMPLICATIONS FOR THE ROLE OF TERRESTRIAL VERTEBRATES IN TROPICAL SYSTEMS

SUGGESTIONS FOR FUTURE RESEARCH

ACKNOWLEDGMENTS

REFERENCES

Chapter 18 ECOSYSTEM DECAY IN CLOSED FOREST FRAGMENTS

OVERVIEW

INTRODUCTION

METHODS

RESULTS

DISCUSSION

ACKNOWLEDGMENTS

REFERENCES

Chapter 19 RESOURCE LIMITATION OF INSULAR ANIMALS: CAUSES AND CONSEQUENCES

OVERVIEW

INTRODUCTION

INSULAR ENVIRONMENTS

TROPICAL ENVIRONMENTS

SPINY RATS AS A CASE STUDY

CONSEQUENCES AND GENERAL IMPLICATIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 20 TROPICAL ARBOREAL ANTS: LINKING NUTRITION TO ROLES IN RAINFOREST ECOSYSTEMS

OVERVIEW

INTRODUCTION

ELEMENTAL AND ECOLOGICAL STOICHIOMETRY OF TROPICAL ARBOREAL ANTS

THE ROLE OF STOICHIOMETRY IN OPPORTUNISTIC ANT–PLANT INTERACTIONS

ANT ASSOCIATIONS WITH ENDOSYMBIONTS

FORAGING FUNCTIONAL GROUPS

NOTE

ACKNOWLEDGMENTS

REFERENCES

Chapter 21 SOIL FERTILITY AND ARBOREAL MAMMAL BIOMASS IN TROPICAL FORESTS

OVERVIEW

INTRODUCTION

SOIL INFERTILITY IN TROPICAL FORESTS

BASIN-WIDE PATTERNS OF PRIMATE BIOMASS

SOIL FERTILITY

EDAPHIC DETERMINANTS OF PRIMATE BIOMASS

SOIL NUTRIENT LIMITATION AND HABITAT PRODUCTIVITY

MAMMAL BIOMASS AND SOIL FERTILITY IN TROPICAL FORESTS

CONCLUDING REMARKS

ACKNOWLEDGMENTS

REFERENCES

Section 5 SECONDARY FOREST SUCCESSION, DYNAMICS, AND INVASION

Chapter 22 PROCESSES CONSTRAINING WOODY SPECIES SUCCESSION ON ABANDONED PASTURES IN THE TROPICS: ON THE RELEVANCE OF TEMPERATE MODELS OF SUCCESSION

OVERVIEW

INTRODUCTION

SCOPE OF THE CHAPTER

OVERVIEW OF PROMINENT MODELS OR CONCEPTUAL FRAMEWORKS OF SUCCESSION

DO STUDIES OF POST-AGRICULTURAL SUCCESSION INCORPORATE OR TEST TEMPERATE MODELS?

THE TWO MAJOR CONSTRAINTS ON TROPICAL POST-AGRICULTURAL SUCCESSION

IS THE NUCLEATION MODEL A VIABLE CONCEPTUAL FRAMEWORK FOR TROPICAL SUCCESSION?

LIMITATIONS OF EXISTING MODELS

AN EMPIRICAL RESEARCH PROGRAM

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 23 CHANCE AND DETERMINISM IN TROPICAL FOREST SUCCESSION

OVERVIEW

INTRODUCTION: SUCCESSIONAL THEMES AND VARIATIONS

THEORETICAL BACKGROUND

AN OVERVIEW OF TROPICAL SECONDARY FOREST SUCCESSION

SUCCESSIONAL DYNAMICS WITHIN INDIVIDUAL FORESTS

RECRUITMENT LIMITATION DURING SUCCESSION

IS THERE AN ENDPOINT TO SUCCESSION?

SUCCESSION IN RELATION TO LANDSCAPE PATTERN

ACKNOWLEDGMENTS

REFERENCES

Chapter 24 EXOTIC PLANT INVASIONS IN TROPICAL FORESTS: PATTERNS AND HYPOTHESES

OVERVIEW

INTRODUCTION

INVASIBLE TROPICAL ECOSYSTEMS

IMPACTS OF EXOTIC PLANTS ON TROPICAL FORESTS

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Section 6 TROPICAL FOREST CONSERVATION

Chapter 25 LINKING INSIGHTS FROM ECOLOGICAL RESEARCH WITH BIOPROSPECTING TO PROMOTE CONSERVATION, ENHANCE RESEARCH CAPACITY, AND PROVIDE ECONOMIC USES OF BIODIVERSITY

OVERVIEW

THREATS TO BIODIVERSITY, BIOPROSPECTING, AND THE CONVENTION ON BIOLOGICAL DIVERSITY

IS BIOPROSPECTING BENEFICIAL FOR DEVELOPING COUNTRIES?

THE PROCESS OF DRUG DISCOVERY RESEARCH

THE INTERNATIONAL COOPERATIVE BIODIVERSITY GROUPS

THE USE OF ECOLOGICAL INSIGHT IN BIOPROSPECTING IN THE PANAMA ICBG

THE SCIENTIFIC OUTPUT OF THE PANAMA ICBG

COMBINING BIOPROSPECTING WITH TECHNOLOGY TRANSFER AND TRAINING IN THE PANAMA ICBG

LINKING BIOPROSPECTING WITH ECONOMIC DEVELOPMENT

WHAT ARE THE OBSTACLES AND THE SOLUTIONS FOR REALIZING ECONOMIC AND SCIENTIFIC DEVELOPMENT THROUGH BIOPROSPECTING?

LINKING BIOPROSPECTING WITH CONSERVATION IN THE PANAMA ICBG

THE FUTURE OF BIOPROSPECTING RESEARCH

ACKNOWLEDGMENTS

REFERENCES

Chapter 26 TROPICAL RAINFOREST CONSERVATION: A GLOBAL PERSPECTIVE

OVERVIEW

INTRODUCTION

MANY THREATS

MANY RAINFORESTS

SAVING THE RAINFORESTS

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 27 ENVIRONMENTAL PROMISE AND PERIL IN THE AMAZON

OVERVIEW

INTRODUCTION

DIRECT THREATS TO THE AMAZON

FUTURE THREATS

AN EXPANDING NETWORK OF RESERVES

CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Chapter 28 CONTRIBUTIONS OF ECOLOGISTS TO TROPICAL FOREST CONSERVATION

OVERVIEW

INTRODUCTION

THE ECOLOGICAL FOUNDATION FOR TROPICAL FOREST CONSERVATION

CONSERVATION SOLUTIONS VARY IN SIZE AND LAND-USE INTENSITIES

CONSERVATION SOLUTIONS REFLECT VARIOUS SOCIOECONOMIC CONTEXTS

CONSERVATION OPPORTUNITIES

CONCLUSIONS: ROLES FOR ECOLOGY AND ECOLOGISTS

REFERENCES

INDEX

This edition first published 2008© 2008 by Blackwell Publishing Ltd

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ISBN: 978-1-4051-1897-2 (paperback)ISBN: 978-1-4051-8952-1 (hardback)

To my parents Walter and Alice Carson: thank you for years of unconditional love and support, and to my son Chris Carson: you have changed the way I see the forest.

Walter P. Carson

PREFACE

It is not hyperbole to say that there has been an explosion of research on tropical forest ecology over the past few decades. The establishment of large forest dynamics plots in tropical forests worldwide, in and of itself, has led to a near revolution in our understanding of forest change. In addition, there has been a substantial increase in the use of models and experiments to test long-standing theories developed to explain the striking patterns found in tropical forests and the putative mechanisms that underlie these patterns. When we started this project, we felt that a comprehensive synthesis of tropical forest community ecology was necessary in order to help the field move forward. Of course, no single volume could do this. Nonetheless, this book is our attempt to make a significant contribution to the field, and to ask anew: What are the main theories in tropical ecology, and which ones are supported or refuted by empirical data? Thus, we have attempted to assemble a volume that describes the most up-to-date findings on the important theories of tropical forest community ecology. We hope that this book accomplishes this goal to the degree possible, while at the same time providing a road map of what we know, what we think we know, and where future research is most needed.

The focus of the chapters in the volume is at the community level because this is where some of the most fundamental questions in tropical ecology exist. Indeed, perhaps the greatest challenge to community ecologist is to explain what processes account for the maintenance of the staggering diversity of plants and animals common in tropical forests around the globe. Still, our emphasis on communities definitely reflects our bias as community ecologists. While we have focused on communities, we certainly recognize the important contributions to tropical ecology that have come from those who study different levels of ecological organization. Indeed, it is difficult to understand communities without understanding the ecology of populations and individuals. We decided to focus on forest communities because, to date, that is where the bulk of research on tropical community ecology has been conducted. We acknowledge that our focus has forced us to omit many important studies. Nonetheless, the emphasis on tropical forest community ecology provides enough material to fill multiple edited volumes, and thus we have attempted to focus on the areas that have received the most empirical attention, along with some topics that are currently nascent, but are rapidly becoming key areas in tropical ecology.

Each chapter in this book was reviewed by at least two relevant experts. We thank these reviewers for their efforts and we are indebted to all of them. We will not list them by name, thus allowing them to remain anonymous. We also thank the production team at Newgen Imaging Systems, and our editors at Blackwell for guiding us through the publication process.

This book, as with all edited volumes, would not have been possible without the dedicated contributions of the authors, each of whom is an expert in his or her respective area of study. For their hard work, truly top-notch contributions, and their patience throughout this process, we owe them a great deal of gratitude. This book is a tribute to their research, along with the research of all of the other scientists whose work is cited in this volume.

Walter P. CarsonPittsburgh, Pennsylvania2007

Stefan A. SchnitzerGamboa, Republic of Panama2007

FOREWORD

The present volume captures the excitement generated by an explosion in tropical forest research. When I was a graduate student in the late 1970s, it seemed to be possible to read every new article published on tropical forests. The ISI Web of Science© confirms this schoolboy memory. Just 289 articles published between 1975 and 1979 included the words “forest*” (for forest, forested or forests) and the name of a tropical country (or tropic*) in their titles. By reading just one or two articles a week, I was able to keep abreast of the entire literature on tropical forests. This would be nearly impossible today. Between 2002 and 2006, 2593 articles met the criteria described above reflecting a nine-fold increase in the rate of publication of tropical forest articles since the late 1970s. This explosion has been driven by new discovery; new theory; new technology; new challenges posed by global change, deforestation and other threats to tropical biodiversity; and ongoing interest in theory posed in the 1970s and earlier. This volume illustrates each of these developments.

In the 1970s, we all “knew” that ants were predatory with the exception of an insignificant few observed at extrafloral nectaries. No one guessed that plant exudates supported most of the great biomass of ants (Chapter 6). Likewise, no one guessed that plants consisted of a mosaic of plant plus endophytic fungi and that the endophytic fungi were hyperdiverse with tens to hundreds of species inhabiting each leaf in the forest (Chapter 15). The roles of herbivorous ants and endophytic fungi are only beginning to be explored, and their implications for forest biology are potentially profound. New theories of chance, dispersal and seed limitation (Chapters 2, 8 and 14) and new tradeoffs postulated between fecundity and habitat tolerance (Chapter 11) also hold the potential to change our understanding of how tropical forest communities are structured and are only now beginning to be explored.

In the 1970s, we would have been mystified by functional (Chapter 10) and phylogenetic (Chapter 20) approaches to plant community ecology and the knowledge base in physiology, morphology and molecular genetics that makes these approaches possible today. Both approaches have the potential to reduce the immense number of species of tropical forest plants to a manageable number of ecologically distinct groups or crucial relationships among species’ traits. Today, we are striving to bring functional, phylogenetic and ecological approaches together for 6000 plus tropical tree species found in the network of large Forest Dynamics Plots maintained by the Center for Tropical Forest Science (Chapter 7).

A graduate student in the late 1970s would have been familiar with the plant favorableness (Chapters 3 and 4), regeneration niche (Chapter 6), Janzen–Connell (Chapter 13) and bottom-up versus top-down hypotheses (Chapters 16–19 and 21) addressed by one third of the chapters in this volume and would be delighted to read the progress summarized here. I was also familiar with the potential of large forest plots – Robin Foster and Steve Hubbell were busy generating excitement for a grand new plot when I was a graduate student on Barro Colorado Island – and it is also a delight to see that potential realized (Chapter 7). Likewise, Phyllis Coley and I were contemporaries as graduate students on BCI as she revolutionized the study of herbivory (and I muddled about with island communities of birds and lizards), and it is a delight to see many of her ideas extended to a new framework to explain herbivory gradients across tropical rainfall gradients (Chapter 5) and to bioprospecting for new pharmaceuticals (Chapter 25).

The final section of this volume (Chapters 22–28) would shock a 1970s graduate student. A potential tropical deforestation crisis was only first publicized in the early 1970s (Gómez-Pompa et al. 1972 Science 177, 762–765). The severity of deforestation in 2007 and the many exacer-bating problems (Chapters 24, 26 and 27) would be entirely unexpected. The potential for solutions through natural secondary succession on abandoned agricultural land (Chapters 22 and 23) and conservation action (Chapter 25) proposed, in some cases, by my peers from the late 1970s on BCI would be equally surprising and heartening.

Where do we go from here? What might a graduate student do in 2007 to have the greatest future impact? There are many answers. Spectacular new data sets are being made available by the Angiosperm Phylogeny Group, by several new efforts to assemble global plant and animal trait data, and by the new remote sensing technologies mobilized in global change research. Those trained to capitalize on these and other similar data sets will make many important contributions.

Simultaneously, we are still in the age of discovery in tropical forest ecology. No one suspected that there might be millions of species of endophytic fungi in tropical leaves until Elizabeth Arnold looked starting in 1996. We are equally ignorant of the roles of myriad other organisms. Even the local point diversity of herbivorous insects remains an unknown. Basic discovery will continue to make many crucial contributions to tropical forest ecology.

Finally, I will return to the nine-fold explosion in tropical forest publication rates mentioned in the first paragraph. The publication rate for extra-tropical forests increased just 4.3-fold over the same time interval. This latitudinal difference has been driven by a 15-fold increase in publication rates for authors from tropical countries. The increase in tropical forest publication rates falls to 5.8-fold when authors with tropical addresses and unknown addresses are excluded. The rapid increase in publication rates for authors from tropical countries is very uneven. Scientists from Brazilian and Mexican institutions increased their rate of tropical forest publications by 71-fold between 1975–1979 and 2002–2006 (from just 9 to 644 articles). Perhaps not surprisingly the authors of this volume include one Brazilian (Chapter 21) and two Mexicans (Chapter 5). Increasingly, scientists from Brazil, Mexico, and other tropical countries will formulate the tropical forest research agenda and determine what research has the greatest future impact. This is a positive development.

S. Joseph WrightSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

LIST OF CONTRIBUTORS

Gregory H. AdlerDepartment of Biology and MicrobiologyUniversity of Wisconsin – OshkoshOshkosh, WIUSA

Jill T. AndersonDepartment of Ecology and Evolutionary BiologyCornell UniversityCorson Hall, Ithaca, NYUSA

A. Elizabeth ArnoldDivision of Plant Pathology and MicrobiologyDepartment of Plant SciencesUniversity of ArizonaTucson, AZUSA

Karina BoegeDepartment of BiologyStanford UniversityStanford, CAUSAandInstituto de EcologíaUniversidad Nacional Autónoma de MéxicoCiudad UniversitariaMéxico

Nicholas BrokawInstitute for Tropical Ecosystem StudiesUniversity of Puerto RicoSan JuanPuerto Rico

Robyn J. BurnhamDepartment of Ecology and Evolutionary BiologyUniversity of MichiganAnn Arbor, MIUSAandMuseum of PaleontologyUniversity of MichiganAnn Arbor, MIUSA

Charles H. CannonDepartment of BiologyTexas Tech. UniversityLubbock, TXUSA

Todd L. CapsonSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

Walter P. CarsonDepartment of Biological SciencesUniversity of PittsburghPittsburgh, PAUSA

Jérôme ChaveLaboratoire Evolution et Diversité BiologiqueUMR 5174 CNRS/UPS, Bâtiment 4R3ToulouseFrance

Robin L. ChazdonDepartment of Ecology and Evolutionary BiologyUniversity of ConnecticutStorrs, CTUSA

Phyllis D. ColeyDepartment of BiologyUniversity of UtahSalt Lake City, UTUSAandSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

Steven C. CookDepartment of BiologyUniversity of UtahSalt Lake City, UTUSAandDepartment of EntomologyTexas A&M UniversityCollege Station, TXUSA

Richard T. CorlettDepartment of Ecology & BiodiversityThe University of Hong KongHong Kong

Luis Cubilla-RiosDepartment of ChemistryUniversity of PanamaPanama CityRepublic of Panama

James W. DallingDepartment of Plant BiologyUniversity of IllinoisUrbana, ILUSA

Diane W. DavidsonDepartment of BiologyUniversity of UtahSalt Lake City, UTUSA

Stuart J. DaviesCenter for Tropical Forest ScienceSmithsonian Tropical Research InstituteApartado 0843-03092BalboaRepublic of Panama

Julie S. DenslowInstitute of Pacific Islands ForestryUSDA Forest ServiceHilo, HIUSA

Saara J. DeWaltDepartment of Biological SciencesClemson UniversityClemson, SCUSA

Rodolfo DirzoDepartment of BiologyStanford UniversityStanford, CAUSA

Lee A. DyerDepartment of Ecology and Evolutionary BiologyTulane UniversityNew Orleans, LAUSA

Daniel A. EmmenDepartment of ZoologyUniversity of PanamaRepublic of Panama

Kenneth FeeleyCenter for Tropical Forest ScienceHarvard University – Arnold ArboretumCambridge, MAUSA

Paul V.A. FineDepartment of Integrative BiologyUniversity of CaliforniaBerkeley, CAUSA

Catherine A. GehringDepartment of Biological SciencesNorthern Arizona UniversityFlagstaff, AZUSA

William GerwickScripps Institution of OceanographyLa Jolla, CAUSA

Mahabir P. GuptaCentro de Estudios Farmacognósticos de la Flora Panameña (CIFLORPAN)Faculty of PharmacyUniversity of PanamaRepublic of Panama

Maria V. HellerSecretaría Nacional de CienciaTecnología e Innovación (SENACYT)Clayton, AnconRepublic of Panama

Stephen P. HubbellDepartment of Ecology and Evolutionary BiologyUniversity of CaliforniaLos Angeles, CAUSAandCenter for Tropical Forest ScienceSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

Robert JohnSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

Kaoru KitajimaDepartment of BotanyUniversity of FloridaGainesville, FLUSAandSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

Thomas A. KursarDepartment of BiologyUniversity of UtahSalt Lake City, UTUSAandSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

William F. LauranceSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of PanamaandBiological Dynamics of Forest Fragments ProjectNational Institute for Amazonian Research (INPA)C.P. 478 ManausBrazil

Egbert G. Leigh JrSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

Joseph MascaroDepartment of Biological SciencesUniversity of Wisconsin-MilwaukeeMilwaukee, WIUSA

Kerry McPhailCollege of PharmacyOregon State UniversityCorvallis, ORUSA

Helene C. Muller-LandauDepartment of Ecology, Evolution and BehaviorUniversity of MinnesotaSt. Paul, MNUSA

Eduardo Ortega-BarríaInstitute of Advanced Scientific Investigations and High Technology Services (INDICASAT)Clayton, AnconRepublic of Panama

John R. PaulDepartment of Biological SciencesUniversity of PittsburghPittsburgh, PAUSA

Carlos A. PeresSchool of Environmental SciencesUniversity of East AngliaNorwichUK

Chris J. PetersonDepartment of Plant BiologyUniversity of GeorgiaAthens, GAUSA

Lourens PoorterForest Ecology and Forest Management GroupWageningen UniversityWageningenThe Netherlands

Richard B. PrimackBiology DepartmentBoston UniversityBoston, MAUSA

Francis E. PutzPrince Bernhard Chair for International Nature ConservationUtrecht UniversityUtrechtThe NetherlandsandDepartment of BotanyUniversity of FloridaGainesville, FLUSA

Dora I. QuirosDepartment of ZoologyUniversity of PanamaRepublic of Panama

Richard H. ReeDepartment of BotanyField Museum of Natural HistoryChicago, ILUSA

Luz I. RomeroInstitute of Advanced Scientific Investigations and High Technology Services (INDICASAT)Clayton, AnconRepublic of Panama

Stefan A. SchnitzerDepartment of Biological SciencesUniversity of Wisconsin-MilwaukeeMilwaukee, WIUSAandSmithsonian Tropical Research InstituteApartado 0843-03092, BalboaRepublic of Panama

Pablo N. SolisCentro de Estudios Farmacognósticos de la Flora Panameña (CIFLORPAN)Faculty of PharmacyUniversity of PanamaRepublic of Panama

John TerborghCenter for Tropical ConservationNicholas School of the Environment and Earth SciencesDuke UniversityDurham, NCUSA

Tad C. TheimerDepartment of Biological SciencesNorthern Arizona UniversityFlagstaff, AZUSA

Jill ThompsonInstitute for Tropical Ecosystem StudiesUniversity of Puerto Rico, San JuanPuerto Rico

Stephen J. TonsorDepartment of Biological SciencesUniversity of PittsburghPittsburgh, PAUSA

Campbell O. WebbArnold Arboretum of Harvard University/Center for Tropical Forest ScienceKotak Pos 223, Bogor 16002Indonesia

Jess K. ZimmermanInstitute for Tropical Ecosystem StudiesUniversity of Puerto Rico, San JuanPuerto Rico

Pieter A. ZuidemaPrince Bernhard Chair for International Nature Conservation and Section of Plant Ecology and BiodiversityUtrecht University, UtrechtThe Netherlands

Section 1

INTRODUCTION

Chapter 1

SCOPE OF THE BOOK AND KEY CONTRIBUTIONS

Stefan A. Schnitzer and Walter P. Carson

Tropical forests are vastly complex systems with a myriad of interactions that ecologists are now just beginning to understand. Thus, for many years tropical forest ecology was, by necessity, largely a descriptive- and demographic-based science. More recently, however, tropical ecologists have begun to test more sophisticated ecological theory. Steve Hubbell has called this a time in tropical ecology where the theoretical rubber finally meets the empirical road. Tropical ecologists are now beginning to unite theory and long-term empirical studies to address a broad array of questions and theories that are of particular importance to tropical systems. These questions include the mechanisms responsible for large-scale patterns of species abundance and distribution, species coexistence and the maintenance of the vast species diversity, trophic interactions, and the dynamics of secondary forest succession, to name a few. These issues are not only important for the advancement of tropical ecology, but are crucial for our overall understanding of basic ecology in any system.

This volume represents a comprehensive synthesis of recent and significant advances in tropical forest community ecology. We have divided the book into five main sections: (1) Large-Scale Patterns in Tropical Communities; (2) Testing Theories of Forest Regeneration and the Maintenance of Species Diversity; (3) Animal Community Ecology and Trophic Interactions; (4) Secondary Forest Succession, Dynamics, and Invasion; and (5) Tropical Forest Conservation. These broad categories encompass some of the most active areas of tropical forest community ecology. We acknowledge that we have omitted some active and important areas of tropical forest research. For example, more chapters in this book were devoted to plants than to animals and some traditionally important areas of tropical ecology (e.g., mutualisms) were not explicitly addressed (but see Arnold Chapter 15, Theimer and Gehring Chapter 17). This bias towards plants, large-scale patterns, and mechanisms for the maintenance of diversity reflects, to some degree, our own expertise as plant ecologists, as well as the abundance of these studies and their impact on tropical forest ecology. The chapters within each of the five major sections of this book represent some of the most recent advances in the field. Below we highlight the importance of each of these chapters.

LARGE-SCALE PATTERNS IN TROPICAL COMMUNITIES

In this section, Chave (Chapter 2) re-examines traditional studies of patterns of vegetation change and diversity at multiple spatial scales (beta-diversity) using new advances in both remote sensing techniques and statistical approaches. He examines theories that inform ecologists about the underlying causes for contrasting patterns of beta-diversity among regions. For example, Chave points out how new approaches can “partition beta-diversity into deterministic and stochastic processes.” Chave’s final conclusion is bold: “The debate over the validity of the neutral theory is now behind us” because there is now little doubt that unpredictability and dispersal limitation play crucial roles in structuring plant communities, as does environmental determinism.

Fine, Ree, and Burnham (Chapter 3) revive and expand the geographic area hypothesis, which predicts that tropical latitudes will have more species because of greater total land area. Although the hypothesis was recently dismissed in the literature (Schemske 2002), Fine et al. demonstrate convincingly that it explains significant variation in latitudinal patterns of tree species richness but only when biome area is integrated over time to include land area fluctuations over millions of years. Future tests of this hypothesis with other growth forms will now have to account for historical shifts in land area.

Paul and Tonsor (Chapter 4) explore the sticky issue regarding the relationship between a species’ age and its range size. This idea can be traced back to Willis (1922) and his studies in Sri Lanka. In the first test using tropical plants (Piper spp.), Paul and Tonsor found a significant positive linear relationship, where species age explained 25% of the variation in geographic range. They call for further research that fully evaluates the shape of the age–area relationship (linear, unimodal, etc.) among many taxa so that its underlying causes can be fully elucidated.

Dirzo and Boege (Chapter 5) develop a new conceptual model of plant defense allocation. This model uses contrasting patterns of foliage availability in strongly seasonal tropical dry forests versus tropical rainforests to predict variable patterns of herbivory and defense. Dirzo and Boege point out that past theoretical frameworks failed to consider how seasonality in rainfall creates highly episodic resource availability. This water availability–phenology hypothesis will likely promote the development of additional models designed to predict patterns of herbivory and damage in other community types that have sharply contrasting patterns of resource availability.

Webb, Cannon, and Davies (Chapter 6) use a phylogenetic approach to explain the taxonomic and ecological composition of tropical trees at multiple scales. By examining the evolution of ecological characters among species within a community, Webb et al. provide the tools to evaluate the relative roles of the biotic and abiotic mechanisms that together act to filter local species composition. Ultimately they seek models that will predict the taxonomic and ecological composition of tropical forest communities; if successful this will be a huge step forward.

Zimmerman, Thompson, and Brokaw (Chapter 7) bring to bear the power of large forest dynamic plots (while confessing their limitations) to tackle the issue of the relative role of neutral dynamics, negative density dependence (NDD), and gap dynamics in explaining high species diversity in tropical forests around the world. They argue persuasively that NDD is pervasive at these sites, thereby weakening the “value of neutral theory as a general explanation” for high species diversity. They reject a major role for gap dynamics for tall-statured tree species, a view that is now well supported, but which contrasts strongly with views from the 1970s and 1980s.

TESTING THEORIES OF FOREST REGENERATION AND THE MAINTENANCE OF SPECIES DIVERSITY

In an engaging, unique, and wide-ranging chapter in the second major section, Leigh (Chapter 8) addresses the relationship between theory and what we really need to know to understand tropical forests. Leigh weighs in on issues ranging from the limitations of neutral theory to how theory addresses the limits on gross primary production. He tells us “what mathematical theory has done” for tropical ecology and why it remains in relatively “crude” form.

Hubbell (Chapter 9) argues that understanding complex ecological systems, such as tropical forests, can best be accomplished using empirical studies to test simple theoretical models that use few free parameters. Hubbell uses the Neutral Theory to illustrate how simple theoretical models make predictions that are consistent with patterns of tree species abundance and diversity that have been observed in tropical forests worldwide. The chapter begins with an entertaining and candid account of the history and development of the Neutral Theory. Hubbell then provides an excellent overview of the theory, beginning with the model in its most simple terms and subsequently adding complexity. Along the way, he explains the key components of the model and emphasizes their unique attributes and importance. Hubbell concludes with some recommendations for the advancement of ecology, including the value of simple, approximate theoretical models, as well as the need for honesty, not advocacy, in testing theory in ecology.

In Chapter 10, Kitajima and Poorter tackle the concept of “the niche” by evaluating the functional basis of resource specialization of tropical trees. They demonstrate that light is partitioned among tree species at all developmental stages and trade-offs exist between growth, survival, and reproduction for many species. The next logical question then becomes, are there similar tradeoffs along other niche axes? If so then there will likely be far more niche opportunities when additional environmental gradients (e.g., fertility and soil moisture) are considered. These findings would appear to challenge the viability of neutral theory.

Muller-Landau (Chapter 11) addresses important trade-offs that are putatively responsible for the maintenance of species diversity. She focuses mostly on the trade-off between competition and colonization, which has garnered much theoretical and empirical attention over the last 50 years. Muller-Landau argues that the available empirical evidence does not support this trade-off for tropical trees, and that other important trade-offs (dispersal–fecundity and tolerance–fecundity) are much more likely candidates to explain plant species coexistence.

Schnitzer, Mascaro, and Carson (Chapter 12) revisit the long-held belief that gaps promote the maintenance of plant species diversity in tropical forests. They concur with Zimmerman et al. (Chapter 7) that gaps do not maintain the diversity of tall-statured shade-tolerant trees. Nonetheless, they argue that gaps may be critical for the persistence of lianas, pioneer trees, and small-statured species trapped in the understory, groups that comprise more than 50% of most tropical floras. In addition, nearly all studies have failed to evaluate the degree to which gaps enhance the fecundity of any life-form, including trees – a potentially important oversight.

The Janzen–Connell hypothesis is one of the most widely accepted explanations for the maintenance of species diversity in tropical forests. Carson et al. (Chapter 13) compile the available literature to evaluate Janzen–Connell. They conclude that there are many examples of distance- and density-dependent effects on survival, growth, and recruitment. There remains, however, a paucity of evidence that these effects maintain diversity at the community level. Additionally Carson et al. argue that falsifying Janzen–Connell is extremely challenging and suggest that the Janzen–Connell effect could be strongest in the least common species.

Dalling and John (Chapter 14) examine the critical role that seed, dispersal, and recruitment limitations play in structuring plant communities. Using simulations based on seed and dispersal traits of pioneers on Barro Colorado Island, Panama, they evaluate whether these limitations minimize competitive interactions, thereby reducing the probability of competitive exclusion. They find that pioneer species appear to be strongly seed limited. However, even the most seed-limited species can become relatively abundant, suggesting that other processes also structure pioneer tree communities.

In Chapter 15, Arnold describes the nascent but increasingly important study of endophytic fungi. To date, endophytes have been found in the photosynthetic tissue of every tropical plant ever examined, and a single tree may harbor thousands of species. The ecological role of endophytes in tropical forests is substantial and complex. Endophytes may act as “environ-mental acquired immune systems” for plants or bolster a plant’s own defense system against pathogens and herbivores. Arnold points out that elucidating the role of natural enemies in structuring plant communities may rest on understanding plant–endophyte–pathogen interactions.

ANIMAL COMMUNITY ECOLOGY AND TROPHIC INTERACTIONS

Although community-level theories in tropical ecology are most commonly tested with plants, they can also be addressed using animals. For instance, in this section, Dyer (Chapter 16) explores the complexity of tritrophic interactions and argues compellingly that the empirical basis for much conventional wisdom within tropical community ecology remains “largely untested.” This includes such standards as tropical consumers are more specialized and that predation is more intense in tropical habitats. Dyer reviews the diversity of trophic cascades and identifies the shortcomings of previous studies. He provides a clear roadmap to how future research will need to integrate solid natural history, phylogenetics, modeling, and experimental approaches.

Theimer and Gehring (Chapter 17) examine the tritrophic interaction among terrestrial vertebrates, tree seedlings, and mycorrhizal fungi using a vertebrate exclusion experiment in an Australian tropical forest. They report that after nearly 5 years, vertebrates reduced seedling species richness via increased rates of density-independent mortality, and concomitantly increased arbuscular mycorrhizal fungi richness via spore dispersal. The authors propose a conceptual model to address how these complex opposing but interrelated effects can alter forest community dynamics and diversity.

Terborgh and Feeley (Chapter 18) exploit an excellent model system of predator-free fragmented forests on small islands in Venezuela to explore the role of complex trophic cascades among plants, herbivores, and their predators. Their results “strongly supported the hypothesis of Hairston, Smith, and Slobodkin,” which posits that regulation by predators prevents herbivores from decimating plant populations. Nevertheless, Terborgh and Feeley ultimately conclude that trophic cascades are “far more complex than implied by simple [tritrophic] models” and that “plant composition is established and maintained by ... numerous interaction links ... between plants and animals.”

Adler (Chapter 19) also examines forest fragments on small islands to evaluate top-down versus bottom-up forces in central Panama. Adler finds that when predators are absent, herbivores (spiny rats) can be resource limited, even in times of resource abundance. He argues that fragmentation will increase conditions where predators are absent, leading to strong trophic cascades. His take-home message: “attempts to categorize herbivore populations as being limited solely by either top-down or bottom-up processes are likely to fail” because both processes operate, but their relative strengths vary seasonally.

Why are arboreal ants the most dominant arthropods of tropical forest canopies in terms of abundance and biomass? Davidson and Cook (Chapter 20) address this and other sizeable questions using the unique approach of ecological stoichiometry, which is the elemental balances (and imbalances) between an organism and its food. The authors use this framework, combined with knowledge of ant digestive anatomy and function, to examine interactions among different ant functional groups and between ants, plants, and trophobionts.

Utilizing an extensive neotropical dataset, Peres (Chapter 21) provides one of the first large-scale tests of the theory that mammalian biomass is directly correlated with soil fertility, which drives plant productivity and food quality (Janzen 1974). Peres’s data support this theory and he provides a predictive model for estimating primate biomass, abundance, and diversity along gradients of soil fertility. He then extends the model to other continental vertebrate communities, urging ecologists to continue to link “soil processes to vertebrate populations ... at large spatial scales.”

SECONDARY FOREST SUCCESSION, DYNAMICS, AND INVASION

In this section, Peterson and Carson (Chapter 22) review and identify the major constraints on woody species colonization into pastures and call for studies that test broad general hypotheses of species turnover. They find that most temperate models of succession fail to apply in tropical regions because these models place too little emphasis on propagule limitation and facilitation. Nonetheless, they propose that with refinements, and with the addition of quantitative models of dispersal, a temperate model of succession from the 1970s (the nucleation model) may accurately explain early patterns of succession in tropical pastures.

Chazdon (Chapter 23) provides a thorough introduction to and review of succession, with a focus on secondary forests. She applies the stages of succession in the tropics developed by Oliver and Larson (1990) for temperate forests: stand initiation, stem exclusion, understory reinitiation, and old-growth phases. This framework is important because it unites conceptual patterns of succession in the tropics with those found in temperate forests. Chazdon questions the notion that a stable climax would ever be reached, thus forcing us “to view all forests as points along a successional continuum.”

Denslow and DeWalt (Chapter 24) examine four likely hypotheses to explain how continental tropical forests resist invasion. Using recently published studies, they conclude that high functional group diversity, high rates of competitive exclusion, and high pest loads may all confer resistance to exotic invasion. Contrary to conventional wisdom, however, high species diversity alone is unlikely to deter invasion. The authors emphasize that the data to test these hypotheses are still relatively weak, and they provide a strategy for future research on this important topic.

TROPICAL FOREST CONSERVATION

The conservation of tropical forests can be promoted by demonstrating their direct value in terms of human services. In this section, Kursar et al. (Chapter 25) outline how basic research can guide bioprospecting, and thus promote tropical forest conservation. The authors show how knowledge of plant species and life-history traits can increase the probability of finding novel active secondary compounds for drug discovery. This exciting approach has resulted in technology transfer, tropical forest conservation, and advance in combating some of the most devastating human diseases of our time.

Corlett and Primack (Chapter 26) take a global perspective on tropical forest conservation and conclude that there are “many rainforests” and “many threats” and that the conservation of the world’s richest ecosystems needs to be a global effort yet reflect clear regional differences. They outline how threats vary among the world’s major forests: Asia, Africa, Madagascar, New Guinea, Central and South America, Australia, and island rainforests. They conclude that “the single most important strategy for protecting intact rainforest communities is to establish – and effectively manage – protected areas.”

While Corlett and Primack took a worldwide focus, Laurance (Chapter 27) hones in on threats and promise for conservation in the Amazon. The outlook is sometimes bleak; in a reference to the biblical book of Revelation, Laurance argues that the four horsemen of the future tropical apocalypse will be uncontrolled agriculture, logging, wildfires, and widespread fragmentation. Annual deforestation is staggering and additional threats include burgeoning immigration and massive economic development. Thankfully, Laurance finds a silver lining in the figurative dark cloud hanging over tropical forest conservation. He suggests that this is also a time of “unparalleled opportunity for conservation” due to expanding networks of reserves, corridors, and other conservation units.

Putz and Zuidema (Chapter 28) argue passionately that ecologists need to examine conservation within a much broader social, economic, and political context. They suggest that in many instances (though not all) “expertocratic approaches,” such as creating a system of walled-off protected reserves, are inappropriate to local, cultural, and political realities. The authors call for expanded research into processes that promote and maintain biodiversity in human-altered landscapes that vary in size from small fragments to large plantations. Are we as ecologists sequestering ourselves away in pristine forests while secondary forests are starved of inquiry?

Overall, we believe that these chapters serve to not only synthesize the current state of knowledge on the ecology of tropical forest communities, but they also point out some of the long-standing but yet unresolved issues in the field. We hope that this volume stimulates additional research in those critical areas.

REFERENCES

Janzen, D.H. (1974) Tropical blackwater rivers, animals, and mast fruiting by the Dipterocarpaceae. Biotropica 6, 69–103.

Oliver, C.D. and Larson, B.C. (1990) Forest Stand Dynamics. McGraw-Hill, Inc., New York.

Schemske, D.W. (2002) Ecological and evolutionary perspectives on the origins of tropical diversity. In R. Chazdon and T. Whitmore (eds), Foundations of Tropical Forest Biology: Classic Papers with Commentaries. University of Chicago Press, Chicago, IL, pp. 163–173.

Willis, J.C. (1922) Age and Area. Cambridge University Press, Cambridge.

Section 2

LARGE-SCALE PATTERNS IN TROPICAL COMMUNITIES

Chapter 2

SPATIAL VARIATION IN TREE SPECIES COMPOSITION ACROSS TROPICAL FORESTS: PATTERN AND PROCESS

Jérôme Chave

OVERVIEW

Understanding the causes of spatial variation in floristic composition is one of the overarching goals of plant ecology. This goal has been challenged by the difficulty of unfolding the spatial component of biodiversity, and of interpreting it biologically, especially in the tropics. Hence until recently, virtually nothing was known about the real impact of land-use change on tropical biodiversity, in spite of the rapid rates of tropical deforestation and habitat loss. This picture has changed dramatically over the past few years, with the development of large-scale inventory projects and the implementation of methods for quantitative analysis of floristic data. Here, I provide an overview of the definitions of spatial floristic turnover, or beta-diversity, and a statistical toolkit for the analysis of beta-diversity. I also contrast ecological theories which underlie the statistical tests. I then review recent empirical studies on plant beta-diversity in tropical forests. This panorama shows that a consensus on field and analytical methods is now being reached. There is a need for careful reinterpretations of published ecological patterns in light of well-formulated ecological hypotheses. Only through ambitious field studies and collaborative approaches will further progress be achieved in this fascinating research area.