Sex Ratios: Concepts and Research Methods

✍ Scribed by Ian C. W. Hardy

• Year: 2002
• Tongue: English
• Leaves: 440
• Edition: 1
• Category: Library

✦ Synopsis

This multi-author volume provides both a conceptual context and an instruction in methods for many aspects of sex ratio research. The book discusses theory, statistical analysis, and genetics, as well as research in one of a wide spectrum of animal, plant, and microbial taxa. Sex Ratios: Concepts and Research Methods is primarily intended for graduate and professional behavioral and evolutionary ecologists in this field, but it will also be useful to biologists building evolutionary models, and researchers analyzing data involving proportions or comparisons across phylogenetically related species.

✦ Table of Contents

Cover......Page 1
Half-title......Page 3
Title......Page 5
Copyright......Page 6
Dedication......Page 7
Contents......Page 9
Contributors......Page 11
Preface and acknowledgements......Page 15
Part 1 Sex ratio theory......Page 17
1.2 Introduction......Page 18
1.3 Models have always been central......Page 19
1.4 Darwin’s argument......Page 20
1.6 Düsing’s model......Page 23
1.8 Genetic models I: tracer genes and the Shaw–Mohler equation......Page 25
1.9 Genetic models II: alleles that determine parental sex ratios......Page 28
1.10.1 Local mate competition......Page 32
1.10.2 Sex ratio conflict in ants......Page 34
1.10.3 Hermaphrodites......Page 36
1.11 Conclusion: diversity in unity......Page 38
References......Page 39
2.2 Introduction......Page 42
2.3 Mechanistic aspects......Page 43
2.3.1 Costs......Page 44
2.3.2 Components......Page 45
2.3.3 Conflicts......Page 47
2.4.1 Evolutionary stability......Page 49
2.4.2 Life history and population dynamics......Page 50
2.4.3 Reproductive values......Page 52
2.4.5 Direct fitness and relatedness......Page 53
2.5.2 Fisher’s model with costly sex ratio control......Page 54
2.5.4 Trivers and Willard’s model with two states......Page 55
2.5.5 Trivers and Willard’s model with costly sex ratio control......Page 56
2.5.6 Multiple allocation components......Page 57
2.5.7 Parent–parent conflict......Page 58
2.6 Appendix: Generalized Shaw–Mohler equation......Page 59
References......Page 60
Part 2 Statistical analysis of sex ratio data......Page 63
3.2 Introduction......Page 64
3.2.1.1 Proportion data and the binomial distribution......Page 67
3.2.2 Questions in sex ratio data analysis......Page 68
3.3 Classical analyses of proportion data......Page 71
3.3.1.2 Example 1: Fish sex ratios......Page 74
3.3.2 General linear models......Page 78
3.3.3.3 Logistic transformation......Page 79
3.4 Generalized linear models......Page 80
3.4.2.3 Link function......Page 81
3.4.3 Determining the best-fit model: maximum-likelihood......Page 82
3.4.4 Overdispersion and underdispersion......Page 83
3.4.4.2 Correcting overdispersion......Page 84
3.4.5 Model simplification......Page 85
3.5 Logistic analysis of sex ratio data......Page 87
3.5.1 Analysis of proportions......Page 88
3.5.1.1 Example 1: Fish sex ratios revisited......Page 89
3.5.1.1.1 SUMMARY OF EXAMPLE 1......Page 91
3.5.2.1 Example 2: Crest size in Crested Auklets......Page 92
3.5.2.1.3 LOGISTIC REGRESSION......Page 94
3.5.2.1.4 PATERNAL CREST LENGTH AND CHICK SEX......Page 95
3.5.3 A worked example: Sex ratio manipulation in zebra finches......Page 96
3.5.4 A case history: Opossum sex ratios......Page 101
3.6 Simulation studies......Page 102
3.6.3 Differences between statistical methods......Page 103
A3.1 Reference sources and statistical packages for GLMs......Page 106
References......Page 107
4.2 Introduction......Page 109
4.3 A brief history of problems in analysis of sex ratios in ants and other social insects......Page 110
4.4 Criteria for appropriate analysis of social insects' sex ratios......Page 111
4.5.1 The general model......Page 112
4.5.2 Applying the general model to real data......Page 119
4.6 The sex investment ratio......Page 123
4.7 How to explain split sex ratios in Lasius niger......Page 124
References......Page 125
5.3 Variance expectations from optimality theory......Page 128
5.4.1 Nonbinomial expectations......Page 129
5.4.2 Binomial expectations......Page 131
5.4.3 Causes of deviations from expected binomial variance......Page 132
5.4.3.1 Overdispersion due to between-clutch variation in p......Page 133
5.5 Precise sex allocation and sex ratio precision......Page 134
5.6.1 Detecting deviations from binomial expectation......Page 137
5.6.1.1 Large clutches......Page 138
5.6.1.2.2 JAMES' METHOD FOR UNEQUAL CLUTCH SIZES......Page 139
5.6.2.1 Specifying alternative hypotheses......Page 140
5.7.1 Control of sex-allocation sequence......Page 141
5.7.2 Exploring the mechanism of sequential allocation......Page 142
5.7.2.2 A caution for sequential effect identification......Page 143
References......Page 145
6.2 Introduction......Page 148
6.3.1 Why do a comparative analysis?......Page 149
6.3.2 Comparative analysis and phylogeny......Page 156
6.4.1 Taxon characteristics......Page 158
6.4.2 Phylogenies......Page 160
6.5.2 Independent contrasts......Page 161
6.5.3 Other methods for continuous data......Page 162
6.5.5 Simulation methods......Page 163
6.6 Analysing comparative data: a worked example......Page 164
6.6.1 An analysis using independent contrasts......Page 165
6.6.2 An analysis by comparison of real with simulated null data......Page 167
A6.1 A comparative biologist’s toolbox......Page 168
A6.1.3 Other software for exploring phylogenies......Page 169
References......Page 170
Part 3 Genetics of sex ratio and sex determination......Page 173
7.3.1 Traditional classification of sex-determining mechanisms......Page 174
7.3.3.1 Genotypic sex determination: male or female heterogamety......Page 175
7.3.3.2 Environmental sex determination......Page 178
7.3.4 Mixed sex determination......Page 179
7.3.5 Consequences for measuring sex ratios......Page 180
7.3.6 A universal mechanism: a model......Page 181
7.4 Evolution of sex-determining mechanisms......Page 182
7.4.2 Simulations of a scenario for the evolution of ESD to GSD......Page 183
References......Page 187
8.2 Introduction......Page 194
8.3 Diversity and its genetic basis......Page 196
8.4 Determination of sex determination......Page 198
8.4.1 Genetics......Page 199
8.4.2 Environment......Page 200
8.5 Complementary sex determination in Hymenoptera......Page 201
8.5.1 Detecting CSD and diploid males......Page 202
8.6 Evolution of sex-determining mechanisms in Armadillidium vulgare......Page 204
References......Page 206
9.2 Introduction......Page 211
9.3 The evolutionary importance of SRDs......Page 212
9.4.1.1 Meiotic drive systems......Page 213
9.4.1.2 B chromosomes......Page 214
9.4.2.1 Parthenogenesis-inducing Wolbachia bacteria......Page 215
9.4.2.3 Maternal sex ratio......Page 216
9.4.2.4 Male-killing agents......Page 217
9.4.2.6 Cytoplasmically induced drive......Page 218
9.5.2 Isofemale lines with phenotype......Page 219
9.5.2.1 Female-biased sex ratio......Page 220
9.5.2.4 Male-biased sex ratios in haplodiploid organisms......Page 221
9.5.4 Hybridization......Page 223
9.6.3 Parthenogenesis, Wolbachia and MSR-like factors......Page 224
9.7 Concluding remarks......Page 225
References......Page 226
Part 4 Animal sex ratios under different life-histories......Page 233
10.2 ‘Usual’ life-histories, and the exceptions......Page 234
10.3 Parasitoid sex ratios......Page 235
10.3.2 Host quality and sex ratio decisions......Page 236
10.4.1.1 Definition, distribution and life-history......Page 237
10.4.1.3 Sibling rivalry and mating structure......Page 238
10.4.2 Heteronomous parasitoids......Page 240
10.4.2.1 Host and egg limitation......Page 241
10.4.2.3 Kin selection......Page 242
10.4.3.1 Single-sex brood production and clutch size......Page 243
10.4.3.2 Single-sex brood production under conditions of host versus egg limitation......Page 244
10.4.3.3 Single-sex brood production and the evolution of clutch size......Page 245
10.5 Conclusions......Page 246
References......Page 247
11.2 Introduction......Page 251
11.3 Evolutionary origins......Page 253
11.4 Selective advantages of arrhenotoky versus pseudo-arrhenotoky......Page 255
11.5 Population mating structure and the evolution of sex-allocation strategies......Page 257
11.6 Sex ratio control......Page 260
11.7 Sex ratio distorters......Page 262
11.8 Future perspectives......Page 264
References......Page 265
12.3 Aphid life cycles......Page 270
12.4 Proximate mechanisms relevant to sex allocation......Page 272
12.5.1.1 Local mate competition......Page 273
12.5.2 Variation in environmental conditions......Page 276
12.5.3 Demographic effects......Page 277
12.6 Future work......Page 278
References......Page 279
13.2 Introduction......Page 282
13.3 Is the sex ratio constrained?......Page 283
13.4 Adaptive models of sex allocation......Page 284
13.4.2 The Trivers-Willard hypothesis and its extensions......Page 286
13.4.3 Local mate competition......Page 288
13.4.4 Local resource competition and enhancement......Page 289
13.4.5 Females should adjust the sex ratio according to their ability to withstand the costs of reproduction......Page 290
13.4.6 Certain brood combinations should be favoured because they prevent fatal combinations of offspring......Page 292
13.5.2 Local resource competition and Trivers-Willard effects in primates......Page 293
13.5.3 Local resource competition and Trivers-Willard effects in antechinuses......Page 294
13.5.4 Zebra finches: a case study in confusion......Page 295
Acknowledgements......Page 296
References......Page 297
14.2 Introduction......Page 303
14.3.1 Population birth sex ratios......Page 304
14.3.2.1 Status: The Trivers-Willard effect......Page 305
14.3.2.2 Evidence for the Trivers-Willard effect......Page 307
14.4.1 The Trivers-Willard effect......Page 308
14.5 Birth sex ratios and postconception investment: summing up......Page 310
14.6.1 Primary sex ratio......Page 311
14.6.4 Mechanisms for the Trivers-Willard effect......Page 313
14.6.5 Mechanism and adaptation......Page 314
14.6.5.1 Inferring adaptation in modern populations from ancestral mechanisms: paternal age as an example......Page 315
14.7.1 Novel environments: should behavioural adaptations be expected in modern humans?......Page 316
14.7.2.1 The relationship between status and reproductive success......Page 317
14.7.2.3 The nature of status......Page 318
14.7.3 Predicting investment: current offspring value or marginal return?......Page 320
Acknowledgements......Page 321
References......Page 322
Part 5 Sex ratios in plants and protozoa......Page 329
15.2 Introduction......Page 330
15.3 Natural history......Page 333
15.4 Theoretical expectations......Page 336
15.5 Tests of theory......Page 338
15.6.2 Field systems......Page 339
15.6.4 Mathematical models......Page 340
15.7.1 Does the sex ratio conform to LMC?......Page 341
15.7.2 Are there conditional sex ratio strategies?......Page 342
15.7.3 Tests of assumptions......Page 343
15.7.3.3 Sampling methods are unbiased......Page 344
15.8 Concluding remarks and future challenges......Page 345
References......Page 346
16.2 Introduction......Page 349
16.4 Measuring trade-offs......Page 350
16.5 Measuring gain curves......Page 351
16.7 The shape of gain curves......Page 353
16.7.1 The male gain curve......Page 354
16.8 A basic model of seed-to-flower ratio in hermaphrodites......Page 355
16.8.4 Calculating the ESS......Page 356
16.9 Effects of selfing on optimal fruit-to-flower ratios......Page 357
16.10 Why do many plants have low fruit-to-flower ratios?......Page 358
16.11 Size-dependent sex allocation......Page 360
References......Page 361
17.2 Introduction......Page 365
17.3.1 Sex-determination mechanisms......Page 366
17.3.2 Mechanisms of sex ratio adjustment......Page 367
17.3.3 Sex ratio variation......Page 368
17.4 Theory for adaptive sex allocation......Page 369
17.5 Methods for estimating sex allocation and the seed sex ratio......Page 372
17.6 Analysis of mean seed sex ratios......Page 373
17.7 New theory: genetic conflict and the sex ratio......Page 374
17.8 Population sex ratios of adult plants......Page 375
17.9 Conclusions......Page 377
References......Page 378
Part 6 Applications of sex ratios......Page 381
18.2 Sexual selection......Page 382
18.3.2 OSR as a tool......Page 384
18.4.1 PRR as a tool......Page 386
18.4.2 Measuring PRR......Page 387
18.5 The dynamics of OSR and PRR......Page 388
18.5.2.1 Environmental factors......Page 389
18.5.2.3 Age and size distributions......Page 391
18.6 OSR influences mate choice......Page 392
18.7 Future developments......Page 393
References......Page 394
19.2 Introduction......Page 399
19.2.1 Extraordinary sex ratios......Page 400
19.2.3 Hamilton’s evidence......Page 401
19.4 What have we learned since Hamilton 1967?......Page 403
19.5 What we do know and should know about individuals......Page 405
19.6 What do we know about the control of sex ratios?......Page 406
19.7 What is the importance of studies of sex ratio evolution?......Page 407
References......Page 409
20.2 The usefulness of sex allocation......Page 415
20.3.2 Local mate competition......Page 416
20.4 Sex allocation and levels of selection......Page 417
20.4.2 Kin selection......Page 418
20.5.1 How do individuals process relevant information about their environment?......Page 419
20.5.3 What can sex allocation tell us about a species or its ecology?......Page 420
20.5.3.3 What limits reproductive success?......Page 421
20.5.4.1 Phenotypic plasticity......Page 422
20.5.4.2 Heritable genetic variation......Page 423
20.6 Conclusions......Page 425
References......Page 426
Index......Page 430