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An Introduction to Evolutionary Ecology

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An Introduction to Evolutionary Ecology An Introduction to Evolutionary Ecology ANDREW COCKBURN Professor of Botany and Zoology School of Life Sciences Australian National University Canberra, Australia ILLUSTRATED BY KARINA HANSEN OXFORD BLACKWELL SCIENTIFIC PUBLICATIONS LONDON EDINBURGH BOSTON MELBOURNE PARIS BERLIN VIENNA Contents PREFACE, xi THE SCOPE OF EVOLUTIONARY ECOLOGY, 1 Patterns in the living world, 2 Why was 1983 so bad for giant pandas?, 2 Different ways of growing up, 3 Why have sex in the sea?, 6 Why does each fig have its own fig wasp?, 7 Interactions between species: a periodic table?, 11 Why are there so many species of beetles?, 12 Darwin's solution to asking why?, 13 Evolution is not a synonym of natural selection, 14 What is natural selection?, 14 Types of selection, 15 Directional, stabilising and disruptive selection, 16 Frequency-dependent selection, 16 Density-dependent and density-independent selection, 18 Hard and soft selection, 19 Natural and artificial selection, 19 Natural and sexual selection, 19 What are fitness and adaptation?, 20 The theory of natural selection is not tautologous, 20 Absolute versus relative prowess, 21 How'do we detect selection and adaptation?, 22 Summary, 23 Further reading, 23 Topics for discussion, 24 THE GENETIC BASIS OF EVOLUTIONARY CHANGE, 25 Genotype and phenotype, 26 Alleles of genes, and dominance, 28 Gene interactions, 28 Nature versus nurture and heritability, 29 How does genetic variation arise?, 32 How do allele frequencies change?, 33 The Hardy—Weinberg Law, 33 Random causes, 34 The Neutral Theory of Molecular Evolution, 36 Major- versus minor-axis polymorphism, 37 Active sites in serine protease inhibitors, 39 Molecular convergence, 40 Gene flow and selection, 41 Molecular drive, 42 The maintenance of variation, 43 The mutation—selection balance, 43 Balancing selection, 45 Antagonistic pleiotropy, 45 Fluctuating environments — temporal change, 46 A case study: host-plant alternation in aphids, 171 The temporal distribution of reproductive effort, 172 Senescence: why grow old?, 173 Evolutionary versus non-evolutionary hypotheses?, 174 Do plants senesce?, 174 Antagonistic pleiotropy versus mutation-accumulation, 175 Semelparity versus iteroparity, 177 . Big-bang reproduction, 180 Terminal reproductive investment, 182 Conservation of reproductive effort?, 183 Latitudinal gradients in brood size, 184 Seed size and number, 186 Covariation of life history traits revisited, 188 Summary, 190 Further reading, 190 Topics for discussion, 190 THE ECOLOGY OF SEX, 191 Why bother? 192 Recombination and genetic diversity, 192 Species selection, 193 The paradoxical cost of sex, 194 The geographic and taxonomic distribution of sex, 195 The main hypotheses, 196 DNA repair, 197 Mutation elimination, 198 Segregation and homozygosity of favourable mutations, 199 Habitat heterogeneity and gene/environment correlations, 199 The Tangled Bank and spatial heterogeneity, 199 The Red Queen and biological heterogeneity, 200 Contrasting the assumptions and predictions, 200 What are males and females?, 203 Sequential hermaphroditism, 204 Simultaneous hermaphroditism, 205 Sex ratio variation, 206 Improved condition affects the fitness of one sex more than the other, 207 Where populations are highly structured, 209 • Local mate competition, 209 Local resource competition and enhancement, 211 Sexual selection and mating systems, 213 Sperm competition, 214 Differences in the opportunity for selection on the sexes, 214 The strange case of the dunnock, 215 Intersexual selection and female choice, 216 Short-term and long-term benefits, 218 But females do occasionally choose genes, 219 Fisher's runaway hypothesis, 219 The condition-dependent handicap hypothesis, 221 Can the hypotheses be tested empirically?, 222 Mate choice in plants?, 225 Summary, 228 Further reading, 229 Topics for discussion, 229 THE ECOLOGICAL CONTEXT OF [ix] SPECIATION, 231 Contents What is a species?, 232 Gene flow, 233 The adaptive landscape, 233 Allopatric speciation, 234 Ecological and genctical conditions promoting divergence, 235 Molecular drive, 235 Sexual selection, 236 Mutualism, 236 Other revolutionary interactions, 237 Reinforcement, 238 The formation of species in small isolated populations, 240 Genetic revolutions, 241 Founder-flush, 241 Genetic transilience, 242 Sexual selection and the founder models, 242 Evaluating the founder models, 243 Parapatric speciation, 242 Sympatric speciation, 245 Is speciation the pivot of morphological evolution?, 247 Stasis and species homogeneity, 249 Autopoicsis and canalisation, 250 Stabilising selection, 251 Gene flow as a constraint and creative force, 252 Summary, 253 Further reading, 253 Topics for discussion, 253 WHY ARE THERE SO MANY SPECIES?, 255 How many species?, 256 Why are some communities more species rich than others?, 258 Types of diversity, 258 Species diversity increases with area, 258 Species diversity decreases with latitude, 262 An area effect?, 262 Time for colonisation?, 262 The species-energy hypothesis, 264 Exceptions to community convergence, 265 Processes within communities and regions?, 265 Competition, 265 Predation and disturbance, 266 The relative importance of predation and competition, 268 Why are there so many species of beetles?, 270 Extinction, 271 Mass extinctions, 271 The Cretaceous/Tertiary boundary, 272 The Permian/Triassic boundary, 274 Are mass extinctions periodic?, 274 Background extinctions, 275 Life cycles in marine invertebrates, 276 The Red Queen and the constancy of extinctions, 277 The correlates of diversification, 278 Adaptive radiations, 278 The bottom-heaviness of clades, 279 A case study: the diversification of the Metazoa, 280 [x] There are more small species, 282 Contents Summary, 283 Further reading, 284 Topics for discussion, 284 10 APPLIED EVOLUTIONARY ECOLOGY, 285 The management of rare and endangered species, 286 What is rarity?, 286 Proximate causes of extinction in very small populations, 290 The Alice effect, 294 Is genetic diversity important?, 294 Inbreeding depression, 295 The problem of outbreeding, 296 Loss of allelcs by drift, 298 Is there a minimum genetically viable population?, 298 The problem of habitat fragmentation, 300 Release of genetically engineered organisms, 301 Stability of recombinant DNA, 302 Rules for introductions, 303 Are genetically engineered organisms different?, 304 Genetic impoverishment of agricultural species, 305 Where will the new genes and agricultural varieties come from?, 306 Solutions: gene banks and the value of biodiversity, 307 Summary, 308 Further reading, 308 Topics for discussion, 309 11 THE SCOPE OF EVOLUTIONARY ECOLOGY REVISITED, 311 The new data sources and tools, 312 Beyond data to theory, 312 Beyond theory to experiment, 313 Assigning frequency, 313 Big questions versus little questions, 313 Seeking applications, 313 REFERENCES, 315 INDEX, 357.
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