Godfrey Hewitt:

Insecta 1. Orthoptera

Grasshoppers and Crickets

1979. V, 170 pages, 22 figures, 16 tables, 16x25cm, 400 g
Sprache: English

ISBN 978-3-443-26009-5, paperback, Preis: 51.00 €

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Schlagworte

cytogenetic • animal • crickets • insekt • grasshopper • Orthoptera • Zytogenetik • Tier • Grille • Heuschrecke • Orthoptera

Inhalte

↓ Introduction
↓ Contents

Introduction nach oben ↑

The contribution of Orthopteran material to our general understanding of the chromosome and cytogenetics has always been significant. From just after the rediscovery of Mendel’s work in the early part of the 20th Century, the large size of the chromosomes and low numbers in the complements of most species have caused investigators to turn again and again to this group as their experimental material. In 1951 White reviewed the important areas where the Orthoptera had furnished evidence, from the pioneer work of McClung (1905) to the then present. Many of the same issues are still with us today albeit in a somewhat different guise, for a series of revolutions in biology in the last 25 years has greatly expanded our understanding of the chromosome, including that most fundamental series of discoveries that established DNA as the genetic material.
Chromosome structure, replication, transcription, movement, pairing, chiasma formation and mutation are fields of great activity at present, and it was initially intended to include sections on these topics. But whilst the Orthoptera can contribute much to these debates, they are general phenomena which properly require a consideration of evidence from many groups of organisms besides the Orthoptera. Furthermore the Orthoptera do not appear to differ greatly from other groups in the general outline of these features Consequently only those aspects where Orthopteran material is particularly relevant will be mentioned and they will be dealt with in the context of chromosomal variation and evolution in the Orthoptera.

Contents nach oben ↑

Acknowledgements V
1 General introduction 1
2 Chromosome variation within species 3
2.1 Introduction 3
2.2 Inversion 4
2.2.1 Centric shifts-transpositions or inversions? 4
2.22 Cytogenetic properties 9
2.2.3 Natural variatio n 14
2.2.4 Establishment and maintenance 15
2.2.5 Keyacris scurra and adaptive topographies 17
2.2.6 Marginal v. central populations 20
2.2.7 Decay of polymorphism and fixation 21
2.3 Interchanges and translocations 23
2.3.1 Cytogenetic properties 23
2.3.2 Isolating mechanisms 25
2.3.3 Terminal associations 27
2.3.4 Tandem fusion 28
2.4 Centric fusion and fission 30
2.4.1 Mechanisms of fusion 30
2.4.2 Mechanisms of fission 32
2.4.3 Meiotic behaviour 36
2.4.4 Spontaneous fusion and fissions 37
2.4.5 Polymorphism, polytypy and chromosome races 39
2.4.6 General considerations 41
2.5 Unequal bivalents and chromosome segments 43
2.5.1 Structural variation and origins 43
2.5.2 Terminal associations 52
2.5.3 Ditactic bivalents 54
2.5.4 Population studies 54
2.6 Supernumerary chromosomes 58
2.6.1 Variation in form 58
2.6.2 Supernumerary or polysomic? 62
2.6.3 Stability and accumulation 63
2.6.4 Association and preferential segregation 65
2.6.5 Effects and functions 66
2.6.6 Population studies 67
2.6.7 Origins and evolution 69
3 Sex chromosomes 70
3.1 Heteropycnosis and inactivation 71
3.2 Variation in form of the X 76
3.3. Neo-XY systems: frequency and form 78
3.4 Intraspecific variation and establishment of neo-XY's 79
3.5 Modification and evolution of neo-XY's 80
3.5.1 Acridoidea 81
3.5.2 Eumastacoidea 83
3.5.3 Tettigonioidea 83
3.5.4 Gryllacridoidea 83
3.5.5 Grylloidea 84
3.6 Neo X1X2Y systems 84
3.6.1 Formation 84
3.6.2 Modification 85
3.6.3 Eneoptera and Euscyrtus 86
3.6.4 Gryllotalpa hexodactyla 86
3.6.5 Differences in frequency 87
4 Parthenogenesis 89
4.1 Occasional parthenogenesis 89
4.2 Regular parthenogenesis 90
4.2.1 Saga pedo 91
4.2.2 Moraba virgo 92
5 Gynandromorphs 95
6 Chromosomes in speciation and hybridisation 98
6.1 Life cycle isolation 9 9
6.2 Courting and mating isolation 101
6.3 Postzygotic isolating mechanisms 102
6.4 Chromosome speciation in the morabines 104
6.4.1 The contact zone in Keyacris scurra 104
6.4.2 Hybrid zones in the viatica group 105
6.4.3 Properties of hybrid zones 109
6.4.4 Origin of parapatric distributions 111
6.4.5 Is speciation possible under parapatry? 114
6.5 Other examples of chromosomal isolation 115
7 Chromosome evolution and taxonomy 118
7.1 Suborder Caelifera: Acridoidea 119
7.2 Eumastacoidea 131
7.3 Tetrigoidea 132
7.4 Tridactyloidea 132
7.5 Suborder Ensifera: Tettigonioidea 133
7.6 Gryhoidea 134
7.7 Gryllacridoidea 137
7.8 Suborder Grylloblattinea: Grylloblattoidea 138
7.9 Conclusion 138
References 139
Species Index 165

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