Evolution in the Dark (eBook)

Prof. Dr. Horst Wilkens Dr. Ulrike Strecker Centrum für Naturkunde – CeNak – Center of Natural History Universität Hamburg – Zoologisches Museum Martin-Luther-King-Platz 3 20146 Hamburg - Germany e-mails: Wilkens@zoologie.uni-hamburg.de; Strecker@uni-hamburg.de  

Acknowledgements 5
Contents 6
1: Evolution in the Dark: Introduction 9
References 10
2: The Role of Rudimentation in Evolution 11
References 19
3: Diversity and the Phylogenetic Age of Cave Species 21
3.1 Mexico and the Peri-Caribbean Islands: A Hot Spot of Aquatic Cave Species Diversity 22
3.2 Strongly Eye-Reduced Cave Species 24
3.3 Lesser and Variably Eye-Reduced Cave Species 28
References 41
4: Surface and Cave Populations of Mexican Astyanax 45
4.1 Astyanax Surface Fish 46
4.2 Astyanax Cave Fish 46
4.3 Phylogeography and Speciation of Surface and Cave Astyanax 52
4.3.1 Invasion of Surface Astyanax from South America and Origin of the Cave Forms 52
4.3.2 Multiple Origin of Cave Forms 56
4.3.3 Population Genetic Diversity of Cave Populations 57
References 58
5: Complexity of Interrelationship Between Astyanax Cave and Surface Fish 61
5.1 General Remarks 62
5.2 Strongly Eye- and Pigment-Reduced Cave Populations 62
5.2.1 Pachón Cave Fish 63
5.2.2 Yerbaniz Cave Fish 65
5.3 Variably Eye- and Pigment-Reduced (VEP) Cave Populations 66
5.3.1 Micos Cave Fish 66
5.3.2 Chica Cave Fish 71
5.3.3 Caballo Moro Cave Fish 74
5.3.4 Molino Cave Fish 75
5.4 Role of Introgressive Hybridization 76
5.5 Speciation and Taxonomy of Astyanax Surface and Cave Fish 78
5.5.1 Surface Fish 78
5.5.2 Cave Fish 80
References 82
6: Regressive and Constructive Traits in Astyanax Surface and Cave Fish 86
6.1 General Remarks 87
6.2 Reproductive Behaviour 89
6.3 Sex Determination 91
6.4 Auditory Capacities 93
6.5 Lateral Line System 93
6.6 Taste 98
6.7 Olfaction 101
6.8 Feeding Behaviour and Food Uptake 101
6.9 Metabolic Adaptation to Permanent or Periodic Low Food Supply 105
6.10 Overall Sleep and Activity Patterns 109
6.11 Egg Yolk Content 111
6.12 Aggressive Behavioural Patterns in Astyanax 113
6.13 Dorsal Light Reaction 119
6.14 Phototactic Behaviour 121
6.15 Pineal Organ 123
6.16 Circadian Rhythm 125
6.17 Fright Reaction 134
6.18 Schooling and Shoaling Behaviour 136
6.19 Scales 139
6.20 Pigmentation 140
6.20.1 Melanophores 140
6.20.2 Brown Gene (Mc1r) 141
6.20.3 Albino Gene (Oca2) 144
6.20.4 Guanine and Carotinoids 145
6.21 Eye 147
6.21.1 Morphology and Histology of the Eyes of the Surface and the SEP Astyanax Cave Fish 147
6.21.2 Visual Pigments 149
6.21.3 Size and Histology of the Eye in the VEP Cave Fish and in the Crossings Between Surface and Cave Fish 151
6.21.3.1 Crossings of the SEP Cave Fish 151
6.21.3.2 VEP Cave Fish and Crossings 152
6.21.3.3 Histology of Eye Structures in the Crossings Between SEP Cave and Surface Fish and in VEP Cave Fish 152
6.21.4 Ontogeny of Eye Development in the SEP Cave Fish 155
6.21.5 Genetic Basis of Eye Development 163
6.21.6 The Role of the Lens in Eye Development 168
6.21.7 Ontogenetic Eye Regression and Head Formation 169
6.21.8 Root Effect 172
6.22 Brain 173
6.23 Comparison of the Genetics of Complex Regressive and Constructive Traits 176
6.23.1 Phenotypic Manifestation and Gene Expression 176
6.23.1.1 Eye 176
6.23.1.2 Melanophore Number 178
6.23.1.3 Feeding Posture 179
6.23.1.4 Number of Free Neuromasts 179
6.23.1.5 Number of Taste Organs 179
6.23.1.6 Sleep Duration 180
6.23.2 Comparison of Phenotypic Manifestation 180
6.23.3 Genetics of Phylogenetically Young VEP Cave Fish 182
6.23.4 Significance of Unproportional Epistatic Gene Effect 184
6.23.5 Nature of Genes Responsible for Complex Traits 185
References 186
7: Mechanisms of Regressive Evolution 197
7.1 Deleterious Risk 198
7.2 Food Limitation and Energy Economy 198
7.3 Quantitative Trait Loci Polarity Test for Selection (Orr´s Sign Test) 199
7.4 Pleiotropy 200
7.4.1 Pleiotropy of Sonic Hedgehog (Shh) Genes 200
7.4.2 Pleiotropy of Neuromodulation (Melanin-Catecholamine Trade-Off Hypothesis) 201
7.4.3 Pleiotropy of Vibration Attraction Behaviour (VAB) and Superficial Neuromasts in the Cave Fish Orbit 203
7.5 Independent Inheritance 204
7.6 Evolutionary Rates of Regressive and Constructive Traits 205
7.7 Reversibility of Regressive Evolution 206
7.8 Variability and Loss: Neutral Mutation Theory 207
7.8.1 Variability of Regressive Traits 209
7.8.2 Loss of Behavioural Traits Not Performed in Darkness 211
7.8.3 Genetic Studies 211
7.9 Variability and Constructive (Darwin´s) Gain 213
7.10 Concluding Remarks 217
References 217