Wallace Arthur is Professor of Zoology at the National University of Ireland, Galway. He is one of the founding editors of the journal Evolution & Development. He obtained his PhD from the University of Nottingham, and held positions at several British universities before moving to Galway in 2004. He has been a Visiting Research Scholar at Harvard University and a Visiting Associate of Darwin College, Cambridge.

• Preface xPart I Foundations 31 Introduction 41.1 From Darwin to Development 41.2 Development; and Evolutionary Changes in Development 91.3 Development and the Realm of Multicellularity 112 What is Evo-Devo? 152.1 Forerunners of Evo-Devo 152.2 Nineteenth-Century Comparative Embryology 162.3 Diverse Antecedents—1900–1980 192.4 Conclusions from History; Messages for the Present 242.5 The Advent of Evo-Devo in the 1980s 252.6 Broad and Narrow Views of Evo-Devo 272.7 Too Few Laws, Too Many Facts? 283 Development, Cells and Molecules 343.1 Analysing the Developing Organism 343.2 Cells and Development: The Basics 373.3 Genes: Structure, Expression and Developmental Function 403.4 Signalling Pathways Within and Between Cells 453.5 Signalling: From Cell to Embryo 483.6 Long-Range Signalling and Developmental Processes 514 Natural Populations 544.1 The Ecological Theatre and the Evolutionary Play 544.2 Types of Creature; Types of Population 554.3 Spatial Structure 604.4 Age Structure 644.5 Genetic Structure 654.6 Natural Selection 67Part II Developmental Repatterning 755 Mutation and Developmental Repatterning 775.1 Mutation in Terms of Altered DNA Sequence 775.2 Mutation in Terms of Proximate Functional Consequences 805.3 Developmental Repatterning at Molecular and Higher Levels 825.4 Developmental Repatterning at the Level of the Whole Organism 885.5 Developmental Repatterning and Fitness 896 Heterochrony 936.1 What is Heterochrony? 936.2 Types and Levels of Heterochrony 946.3 Heterochrony at the Organismic Level 956.4 Heterochrony at the Molecular Level 996.5 Heterochrony and Fitness 1027 Heterotopy 1067.1 What is Heterotopy? 1067.2 Heterotopic Processes Involving Left-Right Asymmetry 1077.3 Heterotopic Processes Involving the A-P and D-V Axes 1127.4 Other Types of Heterotopy 1167.5 Concluding Remarks 1198 Heterometry 1218.1 What is Heterometry? 1218.2 Increasing Relative Size 1228.3 Decreasing Relative Size 1248.4 Bi-directional Heterometry 1288.5 Heterometric Compensation 1329 Heterotypy 1359.1 What is Heterotypy? 1359.2 Altered Products of Developmental Genes 1379.3 Altered Pigmentation 1399.4 Altered Morphology and the Origin of Novelty 1409.5 The Origin of New Cell Types 14410 The Integrative Nature of Repatterning 14810.1 Repatterning is a Complex Process 14810.2 Different Kinds of Repatterning can Produce a Similar Result 14910.3 Compound Repatterning at a Single Level of Organisation 15110.4 The Kind of Repatterning can Change Between Levels of Organisation 15510.5 Categories and Subcategories of Repatterning 15710.6 The Causes of Repatterning 15911 Mapping Repatterning to Trees 16111.1 Pattern, Process, Homology and Trees 16111.2 The Origin(s) of Animal Segmentation 16311.3 The Vertebrate Fin-to-Limb Transition 16911.4 The Origin of Flowers 17611.5 General Conclusions on Repatterning and Selection 179Part III The Direction of Evolution 18312 Adaptation, Coadaptation and Exaptation 18512.1 Natural Selection on a Continuously Variable Character 18512.2 Natural Selection on Two Characters; and the Idea of an Adaptive Landscape 19012.3 Developmental and Functional Coadaptation 19112.4 Morphological Geometry and Selection 19412.5 Long-term Evolution and Exaptation 19613 Developmental Bias and Constraint 20013.1 A Key Question about Evolution’s Direction 20013.2 Making Sure the Question is about Processes, not Terminology 20413.3 Dependence versus Independence of Different Characters 20813.4 Evo-Devo Meets Quantitative Genetics 20913.5 Developmental Bias and ‘Routine’ Evolution 21113.6 Developmental Bias and the Origin of Evolutionary Novelties 21614 Developmental Genes and Evolution 21814.1 The Direction of Evolution at the Developmental/Genetic Level 21814.2 Developmental Genes: An Overview 21914.3 Developmental Genes: Examples 22314.4 The Hox Genes 22514.5 Gene-Level Forms of Developmental Bias and Coadaptation 23014.6 Changes in Regulatory versus Coding Regions of Genes 23115 Gene Co-option as an Evolutionary Mechanism 23415.1 What is Gene Co-option? 23415.2 Co-option in the Evolution of Segments and Eyes 23715.3 Appendage Evolution and Gene Co-option 24115.4 Co-option in the Evolution of Zygomorphic Flowers 24415.5 Evolution of the ‘Genetic Toolkit’ 24515.6 Co-option, Exaptation and Developmental Bias 24916 Developmental Plasticity and Evolution 25216.1 Types of Developmental Plasticity 25216.2 Discrete Variants: Winged and Wingless Forms of Insects 25416.3 Meristic Variation: the Number of Segments in Centipedes 25716.4 Continuous Variation: Plant Growth 25916.5 Plasticity and Developmental Genes 26016.6 The Evolution of Patterns of Plasticity 26117 The Origin of Species, Novelties and Body Plans 27217.1 Is Evolution Scale-dependent? 27217.2 Speciation 27317.3 The Origin of Novelties 28117.4 Body Plans I: Overview 28417.5 Body Plans II: the Origin of the Vertebrates 28517.6 Body Plans III: the ‘Cambrian Explosion’ 28618 The Evolution of Complexity 29118.1 Defining Complexity 29118.2 The Lack of a ‘Law of Increasing Complexity’ 29318.3 Increases in the Complexity of Adults 29918.4 Changes in the Complexity of Life-histories 30218.5 Complexity at the Molecular Level 306Part IV Conclusions 31119 Key Concepts and Connections 31219.1 Introduction: From Original Idea to Mature Scientific Discipline 31219.2 A List of The Book’s Main Points, and the Emergence of Key Concepts 31419.3 How do They Inter-Connect? 31920 Prospects 32720.1 Introduction: From the Present into the Future 32720.2 Molecular Evo-Devo 32720.3 Integrative Evo-Devo and General Evolutionary Theory 33220.4 Wider Challenges 334Glossary 336Appendix 1: A Little Bit of History 355Appendix 2: Naming of Genes and Proteins 359Appendix 3: Geological Time 363Appendix 4: Inferring Evolutionary Trees from Comparative Data 366References 370Index 383

“For that audience, I think it will serve well and I recommend it strongly for university courses.”  (The Quarterly Review of Biology, 6 March2013)“Written is an accessible style, illustrated by many original and specific examples including animals, plants or fossils, this book has the advantage to be an excellent textbook devoted to students studying evolution or to their teachers.  It can be also recommended to anybody interested by the basic concept of evolution.”  (Mammalia, 28 June 2012)"The style is lucid, the illustrations are lavish, and the length is just about right for an undergraduate course resource. Summing Up: Recommended. All students, researchers/faculty, and professionals." (Choice, 1 September 2011) "This exceedingly accessible and very attractive text is illustrated in full color." (Booknews, 1 June 2011)"Although this is a text intended for third level students and professional biologists, Prof Arthur's book brings anyone with more than a passing interest up to date on the mechanisms involved in evolution, and as he notes, we should go easy on the assumptions." (Science Spin, 1 May 2011)

Wallace Arthur is Professor of Zoology at the National University of Ireland, Galway. He is one of the founding editors of the journal Evolution & Development. He obtained his PhD from the University of Nottingham, and held positions at several British universities before moving to Galway in 2004. He has been a Visiting Research Scholar at Harvard University and a Visiting Associate of Darwin College, Cambridge.

• Preface xPart I Foundations 31 Introduction 41.1 From Darwin to Development 41.2 Development; and Evolutionary Changes in Development 91.3 Development and the Realm of Multicellularity 112 What is Evo-Devo? 152.1 Forerunners of Evo-Devo 152.2 Nineteenth-Century Comparative Embryology 162.3 Diverse Antecedents—1900–1980 192.4 Conclusions from History; Messages for the Present 242.5 The Advent of Evo-Devo in the 1980s 252.6 Broad and Narrow Views of Evo-Devo 272.7 Too Few Laws, Too Many Facts? 283 Development, Cells and Molecules 343.1 Analysing the Developing Organism 343.2 Cells and Development: The Basics 373.3 Genes: Structure, Expression and Developmental Function 403.4 Signalling Pathways Within and Between Cells 453.5 Signalling: From Cell to Embryo 483.6 Long-Range Signalling and Developmental Processes 514 Natural Populations 544.1 The Ecological Theatre and the Evolutionary Play 544.2 Types of Creature; Types of Population 554.3 Spatial Structure 604.4 Age Structure 644.5 Genetic Structure 654.6 Natural Selection 67Part II Developmental Repatterning 755 Mutation and Developmental Repatterning 775.1 Mutation in Terms of Altered DNA Sequence 775.2 Mutation in Terms of Proximate Functional Consequences 805.3 Developmental Repatterning at Molecular and Higher Levels 825.4 Developmental Repatterning at the Level of the Whole Organism 885.5 Developmental Repatterning and Fitness 896 Heterochrony 936.1 What is Heterochrony? 936.2 Types and Levels of Heterochrony 946.3 Heterochrony at the Organismic Level 956.4 Heterochrony at the Molecular Level 996.5 Heterochrony and Fitness 1027 Heterotopy 1067.1 What is Heterotopy? 1067.2 Heterotopic Processes Involving Left-Right Asymmetry 1077.3 Heterotopic Processes Involving the A-P and D-V Axes 1127.4 Other Types of Heterotopy 1167.5 Concluding Remarks 1198 Heterometry 1218.1 What is Heterometry? 1218.2 Increasing Relative Size 1228.3 Decreasing Relative Size 1248.4 Bi-directional Heterometry 1288.5 Heterometric Compensation 1329 Heterotypy 1359.1 What is Heterotypy? 1359.2 Altered Products of Developmental Genes 1379.3 Altered Pigmentation 1399.4 Altered Morphology and the Origin of Novelty 1409.5 The Origin of New Cell Types 14410 The Integrative Nature of Repatterning 14810.1 Repatterning is a Complex Process 14810.2 Different Kinds of Repatterning can Produce a Similar Result 14910.3 Compound Repatterning at a Single Level of Organisation 15110.4 The Kind of Repatterning can Change Between Levels of Organisation 15510.5 Categories and Subcategories of Repatterning 15710.6 The Causes of Repatterning 15911 Mapping Repatterning to Trees 16111.1 Pattern, Process, Homology and Trees 16111.2 The Origin(s) of Animal Segmentation 16311.3 The Vertebrate Fin-to-Limb Transition 16911.4 The Origin of Flowers 17611.5 General Conclusions on Repatterning and Selection 179Part III The Direction of Evolution 18312 Adaptation, Coadaptation and Exaptation 18512.1 Natural Selection on a Continuously Variable Character 18512.2 Natural Selection on Two Characters; and the Idea of an Adaptive Landscape 19012.3 Developmental and Functional Coadaptation 19112.4 Morphological Geometry and Selection 19412.5 Long-term Evolution and Exaptation 19613 Developmental Bias and Constraint 20013.1 A Key Question about Evolution’s Direction 20013.2 Making Sure the Question is about Processes, not Terminology 20413.3 Dependence versus Independence of Different Characters 20813.4 Evo-Devo Meets Quantitative Genetics 20913.5 Developmental Bias and ‘Routine’ Evolution 21113.6 Developmental Bias and the Origin of Evolutionary Novelties 21614 Developmental Genes and Evolution 21814.1 The Direction of Evolution at the Developmental/Genetic Level 21814.2 Developmental Genes: An Overview 21914.3 Developmental Genes: Examples 22314.4 The Hox Genes 22514.5 Gene-Level Forms of Developmental Bias and Coadaptation 23014.6 Changes in Regulatory versus Coding Regions of Genes 23115 Gene Co-option as an Evolutionary Mechanism 23415.1 What is Gene Co-option? 23415.2 Co-option in the Evolution of Segments and Eyes 23715.3 Appendage Evolution and Gene Co-option 24115.4 Co-option in the Evolution of Zygomorphic Flowers 24415.5 Evolution of the ‘Genetic Toolkit’ 24515.6 Co-option, Exaptation and Developmental Bias 24916 Developmental Plasticity and Evolution 25216.1 Types of Developmental Plasticity 25216.2 Discrete Variants: Winged and Wingless Forms of Insects 25416.3 Meristic Variation: the Number of Segments in Centipedes 25716.4 Continuous Variation: Plant Growth 25916.5 Plasticity and Developmental Genes 26016.6 The Evolution of Patterns of Plasticity 26117 The Origin of Species, Novelties and Body Plans 27217.1 Is Evolution Scale-dependent? 27217.2 Speciation 27317.3 The Origin of Novelties 28117.4 Body Plans I: Overview 28417.5 Body Plans II: the Origin of the Vertebrates 28517.6 Body Plans III: the ‘Cambrian Explosion’ 28618 The Evolution of Complexity 29118.1 Defining Complexity 29118.2 The Lack of a ‘Law of Increasing Complexity’ 29318.3 Increases in the Complexity of Adults 29918.4 Changes in the Complexity of Life-histories 30218.5 Complexity at the Molecular Level 306Part IV Conclusions 31119 Key Concepts and Connections 31219.1 Introduction: From Original Idea to Mature Scientific Discipline 31219.2 A List of The Book’s Main Points, and the Emergence of Key Concepts 31419.3 How do They Inter-Connect? 31920 Prospects 32720.1 Introduction: From the Present into the Future 32720.2 Molecular Evo-Devo 32720.3 Integrative Evo-Devo and General Evolutionary Theory 33220.4 Wider Challenges 334Glossary 336Appendix 1: A Little Bit of History 355Appendix 2: Naming of Genes and Proteins 359Appendix 3: Geological Time 363Appendix 4: Inferring Evolutionary Trees from Comparative Data 366References 370Index 383

“For that audience, I think it will serve well and I recommend it strongly for university courses.”  (The Quarterly Review of Biology, 6 March2013)“Written is an accessible style, illustrated by many original and specific examples including animals, plants or fossils, this book has the advantage to be an excellent textbook devoted to students studying evolution or to their teachers.  It can be also recommended to anybody interested by the basic concept of evolution.”  (Mammalia, 28 June 2012)"The style is lucid, the illustrations are lavish, and the length is just about right for an undergraduate course resource. Summing Up: Recommended. All students, researchers/faculty, and professionals." (Choice, 1 September 2011) "This exceedingly accessible and very attractive text is illustrated in full color." (Booknews, 1 June 2011)"Although this is a text intended for third level students and professional biologists, Prof Arthur's book brings anyone with more than a passing interest up to date on the mechanisms involved in evolution, and as he notes, we should go easy on the assumptions." (Science Spin, 1 May 2011)

Wallace Arthur is Professor of Zoology at the National University of Ireland, Galway. He is one of the founding editors of the journal Evolution & Development. He obtained his PhD from the University of Nottingham, and held positions at several British universities before moving to Galway in 2004. He has been a Visiting Research Scholar at Harvard University and a Visiting Associate of Darwin College, Cambridge.

• Preface xPart I Foundations 31 Introduction 41.1 From Darwin to Development 41.2 Development; and Evolutionary Changes in Development 91.3 Development and the Realm of Multicellularity 112 What is Evo-Devo? 152.1 Forerunners of Evo-Devo 152.2 Nineteenth-Century Comparative Embryology 162.3 Diverse Antecedents—1900–1980 192.4 Conclusions from History; Messages for the Present 242.5 The Advent of Evo-Devo in the 1980s 252.6 Broad and Narrow Views of Evo-Devo 272.7 Too Few Laws, Too Many Facts? 283 Development, Cells and Molecules 343.1 Analysing the Developing Organism 343.2 Cells and Development: The Basics 373.3 Genes: Structure, Expression and Developmental Function 403.4 Signalling Pathways Within and Between Cells 453.5 Signalling: From Cell to Embryo 483.6 Long-Range Signalling and Developmental Processes 514 Natural Populations 544.1 The Ecological Theatre and the Evolutionary Play 544.2 Types of Creature; Types of Population 554.3 Spatial Structure 604.4 Age Structure 644.5 Genetic Structure 654.6 Natural Selection 67Part II Developmental Repatterning 755 Mutation and Developmental Repatterning 775.1 Mutation in Terms of Altered DNA Sequence 775.2 Mutation in Terms of Proximate Functional Consequences 805.3 Developmental Repatterning at Molecular and Higher Levels 825.4 Developmental Repatterning at the Level of the Whole Organism 885.5 Developmental Repatterning and Fitness 896 Heterochrony 936.1 What is Heterochrony? 936.2 Types and Levels of Heterochrony 946.3 Heterochrony at the Organismic Level 956.4 Heterochrony at the Molecular Level 996.5 Heterochrony and Fitness 1027 Heterotopy 1067.1 What is Heterotopy? 1067.2 Heterotopic Processes Involving Left-Right Asymmetry 1077.3 Heterotopic Processes Involving the A-P and D-V Axes 1127.4 Other Types of Heterotopy 1167.5 Concluding Remarks 1198 Heterometry 1218.1 What is Heterometry? 1218.2 Increasing Relative Size 1228.3 Decreasing Relative Size 1248.4 Bi-directional Heterometry 1288.5 Heterometric Compensation 1329 Heterotypy 1359.1 What is Heterotypy? 1359.2 Altered Products of Developmental Genes 1379.3 Altered Pigmentation 1399.4 Altered Morphology and the Origin of Novelty 1409.5 The Origin of New Cell Types 14410 The Integrative Nature of Repatterning 14810.1 Repatterning is a Complex Process 14810.2 Different Kinds of Repatterning can Produce a Similar Result 14910.3 Compound Repatterning at a Single Level of Organisation 15110.4 The Kind of Repatterning can Change Between Levels of Organisation 15510.5 Categories and Subcategories of Repatterning 15710.6 The Causes of Repatterning 15911 Mapping Repatterning to Trees 16111.1 Pattern, Process, Homology and Trees 16111.2 The Origin(s) of Animal Segmentation 16311.3 The Vertebrate Fin-to-Limb Transition 16911.4 The Origin of Flowers 17611.5 General Conclusions on Repatterning and Selection 179Part III The Direction of Evolution 18312 Adaptation, Coadaptation and Exaptation 18512.1 Natural Selection on a Continuously Variable Character 18512.2 Natural Selection on Two Characters; and the Idea of an Adaptive Landscape 19012.3 Developmental and Functional Coadaptation 19112.4 Morphological Geometry and Selection 19412.5 Long-term Evolution and Exaptation 19613 Developmental Bias and Constraint 20013.1 A Key Question about Evolution’s Direction 20013.2 Making Sure the Question is about Processes, not Terminology 20413.3 Dependence versus Independence of Different Characters 20813.4 Evo-Devo Meets Quantitative Genetics 20913.5 Developmental Bias and ‘Routine’ Evolution 21113.6 Developmental Bias and the Origin of Evolutionary Novelties 21614 Developmental Genes and Evolution 21814.1 The Direction of Evolution at the Developmental/Genetic Level 21814.2 Developmental Genes: An Overview 21914.3 Developmental Genes: Examples 22314.4 The Hox Genes 22514.5 Gene-Level Forms of Developmental Bias and Coadaptation 23014.6 Changes in Regulatory versus Coding Regions of Genes 23115 Gene Co-option as an Evolutionary Mechanism 23415.1 What is Gene Co-option? 23415.2 Co-option in the Evolution of Segments and Eyes 23715.3 Appendage Evolution and Gene Co-option 24115.4 Co-option in the Evolution of Zygomorphic Flowers 24415.5 Evolution of the ‘Genetic Toolkit’ 24515.6 Co-option, Exaptation and Developmental Bias 24916 Developmental Plasticity and Evolution 25216.1 Types of Developmental Plasticity 25216.2 Discrete Variants: Winged and Wingless Forms of Insects 25416.3 Meristic Variation: the Number of Segments in Centipedes 25716.4 Continuous Variation: Plant Growth 25916.5 Plasticity and Developmental Genes 26016.6 The Evolution of Patterns of Plasticity 26117 The Origin of Species, Novelties and Body Plans 27217.1 Is Evolution Scale-dependent? 27217.2 Speciation 27317.3 The Origin of Novelties 28117.4 Body Plans I: Overview 28417.5 Body Plans II: the Origin of the Vertebrates 28517.6 Body Plans III: the ‘Cambrian Explosion’ 28618 The Evolution of Complexity 29118.1 Defining Complexity 29118.2 The Lack of a ‘Law of Increasing Complexity’ 29318.3 Increases in the Complexity of Adults 29918.4 Changes in the Complexity of Life-histories 30218.5 Complexity at the Molecular Level 306Part IV Conclusions 31119 Key Concepts and Connections 31219.1 Introduction: From Original Idea to Mature Scientific Discipline 31219.2 A List of The Book’s Main Points, and the Emergence of Key Concepts 31419.3 How do They Inter-Connect? 31920 Prospects 32720.1 Introduction: From the Present into the Future 32720.2 Molecular Evo-Devo 32720.3 Integrative Evo-Devo and General Evolutionary Theory 33220.4 Wider Challenges 334Glossary 336Appendix 1: A Little Bit of History 355Appendix 2: Naming of Genes and Proteins 359Appendix 3: Geological Time 363Appendix 4: Inferring Evolutionary Trees from Comparative Data 366References 370Index 383

“For that audience, I think it will serve well and I recommend it strongly for university courses.”  (The Quarterly Review of Biology, 6 March2013)“Written is an accessible style, illustrated by many original and specific examples including animals, plants or fossils, this book has the advantage to be an excellent textbook devoted to students studying evolution or to their teachers.  It can be also recommended to anybody interested by the basic concept of evolution.”  (Mammalia, 28 June 2012)"The style is lucid, the illustrations are lavish, and the length is just about right for an undergraduate course resource. Summing Up: Recommended. All students, researchers/faculty, and professionals." (Choice, 1 September 2011) "This exceedingly accessible and very attractive text is illustrated in full color." (Booknews, 1 June 2011)"Although this is a text intended for third level students and professional biologists, Prof Arthur's book brings anyone with more than a passing interest up to date on the mechanisms involved in evolution, and as he notes, we should go easy on the assumptions." (Science Spin, 1 May 2011)