Contents

List of Illustrations	xvii
List of Tables	xxiii
List of Boxes	xxv
Preface	xxvii
PART 1
EARLY PROBLEMS, EARLY SOLUTIONS	1
1 Speciation, Adaptive Radiation, and Evolution	3
Introduction	3
Adaptive Radiation of Darwin’s Finches	4
Species and Speciation	9
Daphne	10
Evolution Observed	12
Chapters of the Book	15
Summary	16
2 Daphne Finches: A Question of Size	17
Introduction	17
Testing the Hypothesis	21
AVAILABILITY OF FOOD	22
DIETS OF G. FORTIS AND G. FULIGINOSA	22
DIFFERENCES IN SEED SUPPLY	27
G. FULIGINOSA ON LOS HERMANOS	28
Association between Beak Size and Diet	30
Adaptive Landscapes	30
Can G. scandens Be Ignored?	35
Why Is G. fuliginosa Absent?	37
Discussion	39
Summary	39
3 Heritable Variation	41
Introduction	41
Estimating Heritable Variation	43
Heritable Variation	44
Potential Biases	46
EXTRA-PAIR PATERNITY	46
MISIDENTIFIED PATERNITY	47
MATERNAL EFFECTS	47
GENOTYPE × ENVIRONMENT CORRELATION	48
CONCLUSIONS ON BIAS	49
Heritabilities: A Comparison of Species	49
Summary	53
4 Natural Selection and Evolution	55
Introduction	55
Expectations	56
Natural Selection	57
CAUSES OF SELECTIVE MORTALITY	59
THE TARGETS OF SELECTION	61
Evolution in Response to Selection	62
Selection Occurs Repeatedly	63
Selection Oscillates in Direction	67
Evolutionary Response	73
Selection in Opposite Directions	74
Conclusions	75
Summary	75
5 Breeding Ecology and Fitness	77
Introduction	77
Basic Breeding Biology	78
ANNUAL VARIATION IN REPRODUCTION IN RELATION TO RAIN	81
Predicting Reproductive Success	87
THE COHORTS OF 1975	87
FOUR LATER COHORTS	89
THE CONTRIBUTION OF MORPHOLOGY TO FITNESS	90
THE CONTRIBUTION OF OFFSPRING TO PARENTAL FITNESS	93
LONGEVITY	93
INBREEDING	96
Variation in Fitness	97
Discussion	99
Summary	100
PART 2
DEVELOPING A LONG-TERM PERSPECTIVE	101
6 A Potential Competitor Arrives on Daphne	103
Introduction	103
Founder Event	105
CAUSES	105
First Few Generations	106
INBREEDING	107
FITNESS COSTS OF INBREEDING	107
IMMIGRATION	108
SELECTION	109
Genetic Diversity	111
LOSSES AND GAINS OF ALLELES	112
THE SOURCE OF IMMIGRANTS	112
NONRANDOM COLONIZATION	115
Song	115
Colonization Success	117
Summary	119
7 Competition and Character Displacement	122
Introduction	122
Competition and Diet Overlap	123
Effects of Competition on Survival	123
Character Displacement	125
STRENGTH OF SELECTION	128
THE CAUSAL ROLE OF G. MAGNIROSTRIS	129
High impact on food supply	130
Superior feeding efficiency on shared component of the diet	130
Parallel decline due to starvation	130
Key difference between 1977 and 2004	132
EVOLUTION OF A DISPLACED CHARACTER	132
G. FORTIS AND SCANDENS COMPARED	133
Some Implications	134
Summary	136
8 Hybridization	138
Introduction	138
Background	139
Frequency of Hybridization	141
Causes of Hybridization	141
A SCARCITY OF CONSPECIFIC MATES	141
IMPRINTING	143
SONG INHERITANCE	143
PERTURBATION OF IMPRINTING	149
G. MAGNIROSTRIS	153
Fitness Consequences of Hybridization	156
VIABILITY	156
FERTILITY	160
OVERALL FITNESS	160
The Mating Pattern of Hybrids	163
Conclusions	164
Summary	165
9 Variation and Introgression	166
Introduction	166
Morphology of Hybrids	169
Effects of Hybridization on Variation	169
COMPARISON OF G. FORTIS AND G. SCANDENS	171
Conspecific Gene Flow	174
Hybridization versus Mutation	174
Correlations	176
Evolutionary Potential	177
Discussion	178
Summary	179
PART 3
HYBRIDIZATION AND SPECIATION	181
10 Long-Term Trends in Hybridization	183
Introduction	183
A Question of Identity	184
BLURRING OF GENETIC DISTINCTIONS	185
BLURRING OF MORPHOLOGICAL DISTINCTIONS	188
Morphological Convergence	190
Frequencies of Hybrids	191
Morphological Variation	192
ALLOMETRY	194
Genetic Convergence	196
Two Species or One?	199
Plumage and Behavior	201
Discussion	201
Summary	204
11 Long-Term Trends in Natural Selection	205
Introduction	205
Selection	207
G. FORTIS	207
G. SCANDENS	207
ECOLOGICAL CAUSES	207
STABILIZING SELECTION	211
Morphological Trends	211
G. FORTIS	211
G. SCANDENS	213
G. MAGNIROSTRIS	216
THE POSSIBLE ROLE OF SELECTION ON G. MAGNIROSTRIS	219
IMMIGRATION	223
THE CAUSE OF THE BEAK-SIZE TREND	224
Allometry of Means	224
Natural and Artificial Selection	226
Conclusion	226
Summary	228
12 Speciation	229
Introduction	229
Morphological Transformation in Speciation	230
SPECIES THAT DIFFER IN SIZE	231
SPECIES THAT DIFFER IN SHAPE	232
Genetic Transformation in Speciation	234
Growth after Hatching	236
Rapid Tempo of Speciation	238
Interactions in Sympatry	239
A MECHANISM PRODUCING SONG DIVERGENCE	241
Summary	243
13 Speciation by Introgressive Hybridization	245
Introduction	245
A Hybrid Arrives on Daphne	247
Descendants	248
PHASE 1: THE START OF A NEW LINEAGE	248
The phenotypic uniqueness of 5110	250
PHASE II: GENERATIONS 1–3	251
PHASE III: ENDOGAMY AND REPRODUCTIVE ISOLATION	253
Origin of Reproductive Isolation	260
Fate of the A Line of Descent	260
Success of the Lineage So Far	263
INTRINSIC FACTORS	263
EXTRINSIC FACTORS	265
Future Prospects	265
Summary	267
PART 4
SYNTHESES	269
14 The Future of Finches on Daphne	271
Introduction	271
The Past as Context of the Present	272
MERGE-AND-DIVERGE DYNAMICS	275
The Present as a Guide to the Future	275
GLOBAL WARMING AND GALÁPAGOS	276
Finch Futures	279
MEANS AND EXTREMES	279
G. FORTIS, SCANDENS, AND FULIGINOSA	280
G. MAGNIROSTRIS	280
HYBRID LINEAGE	281
INVASIVE PLANT SPECIES AND DISEASE	283
Genomes for the Future	284
Summary	286
15 Themes and Issues	287
Introduction	287
Speciation, Selection, and Hybridization	289
EVOLUTION	289
ECOLOGICAL IMPORTANCE OF FOOD: THE DAPHNE PERSPECTIVE	290
BEHAVIORAL BARRIER TO INTERBREEDING	291
SIZE AND HYBRIDIZATION	293
PHYLOGENETIC IMPLICATIONS OF HYBRIDIZATION	294
EPHEMERALITY OF SPECIES	294
PREDICTABILITY AND EVOLVABILITY	296
Overview	298
Summary	299
16 Generalization	300
Generalizing When N = 1	300
THE SMALL POPULATION SYNDROME	301
THE MEDIUM POPULATION SYNDROME	302
LARGE ISLANDS	303
BEYOND GALÁPAGOS	304
THE SPECTER OF EXTINCTION, THE BIG UNKNOWN	306
Summary	308
17 Epilogue	310
Reflections on the Value of Long-Term Studies	310
LONG-TERM DYNAMICS OF A COLOR POLYMORPHISM	311
RARE EVENTS AND THEIR CONSEQUENCES	315
CHANGES IN PERSPECTIVE	316
Coda	319
Appendixes	321
Appendix 1.1 Daphne Plants	321
Appendix 1.2 Measurements of Finches	323
Appendix 1.3 Other Species of Darwin’s Finches	324
Appendix 3.1 Mapping Breeding Locations	324
Appendix 3.2 Annual Changes in Measurements	324
Appendix 5.1 Extra-pair Mating	326
Appendix 5.2 Visitors and Predation	327
Appendix 9.1 Variation and Mortality	328
Appendix 10.1 On the Dangers of Extrapolation	331
Appendix 10.2 Plumage	331
Appendix 11.1 Samples of Measurements for Selection Analyses	332
Appendix 13.1 Identification of Breeders	335
Appendix 17.1 Nestling Beak Color Polymorphism	335
Abbreviations	341
Glossary	343
References	353
Subject Index	389