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List of Illustrations xi List of Tables xv Preface xvii CHAPTERONE: The Biodiversity Problem and Darwin's Finches 1 Biodiversity 1 TheChoice of Organisms 2 Darwin's Finches 3 Diversity of Darwin's FinchSpecies 5 Species and Populations 8 Overview of the Book 11 CHAPTERTWO: Origins and History 13 Introduction 13 Phylogeny 14 Ancestors 16 TheTime of Arrival 16 Colonization 17 The Ecological Theater 18 A Change ofScenery 21 The Evolutionary Play 22 Recent History 22 Summary 25CHAPTER THREE: Modes of Speciation 26 The Formation of New Species 26 TwoGroups from One 27 Divergence in Allopatry 28 Coexistence in Sympatry 29Sympatric Speciation 30 Parapatric Speciation 31 Testing the Models 33Summary 33 CHAPTER FOUR: Colonization of an Island 35 Speciation: TheInitial Split 35 Establishment of a New Population 35 Founder Effects:Expectations from Theory 36 A Colonization Event 38 Inbreeding 39Recurrent Immigration 39 An Alternative Phenology of Founder Effects 42Conclusion 42 Species Elsewhere 44 Summary 45 CHAPTER FIVE: NaturalSelection, Adaptation, and Evolution 46 Adaptation 46 Beak Sizes and Diets47 Adaptive Evolution When the Environment Changes 50 Natural Selection 52Evolution 54 Oscillating Directional Selection 55 Extrapolating from Shortto Long Term 58 The Sources of Variation 58 How Beaks Are Formed 59 Depthand Width 59 Length 62 Summary 63 CHAPTER SIX: Ecological Interactions65 Introduction 65 Competition 66 Patterns of Coexistence 66 DietsInferred from Beaks 67 Interpreting the Patterns 67 Character Displacementand Release 68 Character Displacement Observed 68 The Competitive Role ofG. Magnirostris 69 Selection under Contrasting Conditions 73 Evolution ofCharacter Displacement 73 Summary 75 CHAPTER SEVEN: ReproductiveIsolation 76 Pre-mating Barrier to Interbreeding 76 Factors Involved in theDiscrimination between Species 76 Beaks 77 Song 77 Learning 79 SongDifferences between Species 80 Song Divergence in Allopatry 81 Adaptationto Habitat 83 Change of Songs as a Consequence of Morphological Divergence84 The Role of Chance 86 Simulating Secondary Contact 88 Summary 91CHAPTER EIGHT: Hybridization 92 Introduction 92 Hybridization 92 WhyHybridization Occurs 93 When Hybridization Does Not Occur 96 Hybrid Fitness97 Introgression on Daphne Major 100 Introgression in the Archipelago 103Reinforcement 103 Reproductive Character Displacement 105 EvolutionarySignificance of Introgression 106 Summary 107 CHAPTER NINE: Species andSpeciation 108 Introduction 108 From Process to Product:What Is a Species?109 A Working Definition 110 How Many Species of Darwin's Finches? 111Certhidea olivacea: One Species or Two? 112 Geospiza difficilis: One Speciesor Three? 113 From Product Back to Process 114 Fission and Fusion 116Summary 119 CHAPTER TEN: Reconstructing the Radiation of Darwin'sFinches 120 Introduction 120 The Shape of the Radiation 121 Speciation andExtinction 123 Speciation 125 Extinction 126 Implications for Phylogeny127 Adaptive Landscape 128 A Pattern of Ecological Segregation 133Specialization 134 The Buildup of Complex Communities 134 Summary 135CHAPTER ELEVEN: Facilitators of Adaptive Radiation 137 Introduction 137Environmental Opportunity 138 Geographical Suitability 139 EcologicalOpportunity 140 High Diversification Potential 142 Behavioral Flexibility142 Introgressive Hybridization 145 Hybridization and Animal Breeding 146Environmental Conditions Conducive to Introgression 146 Finches versusMockingbirds 148 Summary 150 CHAPTER TWELVE: The Life History ofAdaptive Radiations 152 Introduction 152 The First Stage of AdaptiveRadiation 153 The Second Stage of Adaptive Radiation 154 Haldane's Rule 157The Third Stage of Adaptive Radiation 158 Synthesis 160 Summary 162CHAPTER THIRTEEN: Summary of the Darwin's Finch Radiation 163 What Happenedand Why 163 What Is Missing? 165 Epilogue 166 Glossary 168 References175 Author Index 201 Subject Index 210