List of Illustrations xi
List of Tables xv
Preface xvii

CHAPTER ONE: The Biodiversity Problem and Darwin's Finches 1
Biodiversity 1
The Choice of Organisms 2
Darwin's Finches 3
Diversity of Darwin's Finch Species 5
Species and Populations 8
Overview of the Book 11

CHAPTER TWO: Origins and History 13
Introduction 13
Phylogeny 14
Ancestors 16
The Time of Arrival 16
Colonization 17
The Ecological Theater 18
A Change of Scenery 21
The Evolutionary Play 22
Recent History 22
Summary 25

CHAPTER THREE: Modes of Speciation 26
The Formation of New Species 26
Two Groups from One 27
Divergence in Allopatry 28
Coexistence in Sympatry 29
Sympatric Speciation 30
Parapatric Speciation 31
Testing the Models 33
Summary 33

CHAPTER FOUR: Colonization of an Island 35
Speciation: The Initial Split 35
Establishment of a New Population 35
Founder Effects: Expectations from Theory 36
A Colonization Event 38
Inbreeding 39
Recurrent Immigration 39
An Alternative Phenology of Founder Effects 42
Conclusion 42
Species Elsewhere 44
Summary 45

CHAPTER FIVE: Natural Selection, Adaptation, and Evolution 46
Adaptation 46
Beak Sizes and Diets 47
Adaptive Evolution When the Environment Changes 50
Natural Selection 52
Evolution 54
Oscillating Directional Selection 55
Extrapolating from Short to Long Term 58
The Sources of Variation 58
How Beaks Are Formed 59
Depth and Width 59
Length 62
Summary 63

CHAPTER SIX: Ecological Interactions 65
Introduction 65
Competition 66
Patterns of Coexistence 66
Diets Inferred from Beaks 67
Interpreting the Patterns 67
Character Displacement and Release 68
Character Displacement Observed 68
The Competitive Role of G. Magnirostris 69
Selection under Contrasting Conditions 73
Evolution of Character Displacement 73
Summary 75

CHAPTER SEVEN: Reproductive Isolation 76
Pre-mating Barrier to Interbreeding 76
Factors Involved in the Discrimination between Species 76
Beaks 77
Song 77
Learning 79
Song Differences between Species 80
Song Divergence in Allopatry 81
Adaptation to Habitat 83
Change of Songs as a Consequence of Morphological Divergence 84
The Role of Chance 86
Simulating Secondary Contact 88
Summary 91

CHAPTER EIGHT: Hybridization 92
Introduction 92
Hybridization 92
Why Hybridization Occurs 93
When Hybridization Does Not Occur 96
Hybrid Fitness 97
Introgression on Daphne Major 100
Introgression in the Archipelago 103
Reinforcement 103
Reproductive Character Displacement 105
Evolutionary Significance of Introgression 106
Summary 107

CHAPTER NINE: Species and Speciation 108
Introduction 108
From Process to Product: What Is a Species? 109
A Working Definition 110
How Many Species of Darwin's Finches? 111
Certhidea olivacea: One Species or Two? 112
Geospiza difficilis: One Species or Three? 113
From Product Back to Process 114
Fission and Fusion 116
Summary 119

CHAPTER TEN: Reconstructing the Radiation of Darwin's Finches 120
Introduction 120
The Shape of the Radiation 121
Speciation and Extinction 123
Speciation 125
Extinction 126
Implications for Phylogeny 127
Adaptive Landscape 128
A Pattern of Ecological Segregation 133
Specialization 134
The Buildup of Complex Communities 134
Summary 135

CHAPTER ELEVEN: Facilitators of Adaptive Radiation 137
Introduction 137
Environmental Opportunity 138
Geographical Suitability 139
Ecological Opportunity 140
High Diversification Potential 142
Behavioral Flexibility 142
Introgressive Hybridization 145
Hybridization and Animal Breeding 146
Environmental Conditions Conducive to Introgression 146
Finches versus Mockingbirds 148
Summary 150

CHAPTER TWELVE: The Life History of Adaptive Radiations 152
Introduction 152
The First Stage of Adaptive Radiation 153
The Second Stage of Adaptive Radiation 154
Haldane's Rule 157
The Third Stage of Adaptive Radiation 158
Synthesis 160
Summary 162

CHAPTER THIRTEEN: Summary of the Darwin's Finch Radiation 163
What Happened and Why 163
What Is Missing? 165

Epilogue 166
Glossary 168
References 175
Author Index 201
Subject Index 210

Peter R. Grant is the Class of 1877 Professor of Zoology at Princeton University. His books include Ecology and Evolution of Darwin's Finches (Princeton).

B. Rosemary Grant is a senior research scholar in the Department of Ecology and Evolutionary Biology at Princeton University. She is the coauthor, with Peter R. Grant, of Evolutionary Dynamics of a Natural Population: The Large Cactus Finch of the Galapagos.