In the past years, much work has been carried out on either life-history evolu­ tion or structure and function of food webs. However, most studies dealt with only one of these areas and often touched upon the other only marginally. In this volume, we try to synthesize aspects of both disciplines and will concen­ trate on how the interactions between organisms depend on their life-history strategies. Since this is a very comprehensive topic, this volume will focus on vertical interactions to remain within a clearly arranged field. We present some scenaria based on life-history variation of resource and consumer, and show how particular patterns of life-history combinations will lead to particular patterns in trophic relationships. We want to deal with the selective forces underlying these patterns: the degree of specificity of the consumers deter­ mines the dependence on its resource, and its adaptation to the spatial and temporal availability of the resource. In this respect, the spatial structure of the resource and its "quality" may play an important role. The impact of natural enemies is another important selective force which may influence the evolu­ tion of interactions between species and the structure of communities. Here, the acquirement of an enemy-free space may provide selective adavantages. The importance of the impact of enemies is also expressed by the development of numerous and sometimes very subtle defense strategies. This will be dem­ onstrated especially for various aspects of chemical ecology.

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A Plant-Insect Relationships: Life-History and Evolution of Tephritid Flies.- 1 The Sympatric Origin of Phytophagous Insects.- 1.1 Introduction.- 1.2 The Debate over Allopatric and Nonallopatric Speciation.- 1.2.1 Contrasting Views on the Importance of Geographic Isolation.- 1.2.2 Gene Flow and Sympatric Speciation.- 1.3 The Plausibility of Sympatric Speciation.- 1.3.1 Allopatric or Sympatric Speciation in the Beetle Genus Ophraella?.- 1.3.2 Allopatric or Sympatric Speciation in the Tephritid Fruit Fly Genus Rhagoletis?.- 1.3.2.1 Biology and Distribution.- 1.3.2.2 Sympatric Host Race Formation.- 1.3.2.3 Sympatric Speciation: a Molecular Perspective.- 1.3.2.4 No History of Geographic Isolation Between Sister Species.- 1.4 Peripatric Speciation Unsupported by Convincing Evidence.- 1.5 Sympatric Speciation and Negative Trade-Offs.- 1.6 Phytophagous Species and Host Races: Is There a Difference?.- 1.6.1 Species as Genotypic Clusters.- 1.6.2 Genotypic Clusters, Allopatric Populations, and the "Test of Sympatry".- 1.6.3 What is a Host Race?.- 1.6.4 When Does a Host Race Become a Species?.- 1.7 Conclusions.- References.- 2 Host Race Formation in Tephritis conura: Determinants from Three Trophic Levels.- 2.1 Introduction.- 2.2 Resource Utilization in Different Host Plants.- 2.3 Mortality Risks.- 2.3.1 Bud Abortion.- 2.3.2 Intraspecific Competition.- 2.3.3 Parasitization Risks in Different Host Plants.- 2.4 Differentiation Among T. conura Populations.- 2.4.1 Fly and Host-Plant Phenology.- 2.4.2 Mating Preferences.- 2.4.3 Larval Development in Different Host Plants.- 2.4.4 Morphological Adaptations in Different Populations.- 2.5 Morphological and Genetic Differentiation Between Populations.- 2.6 Conclusions.- References.- 3 Symphagy Among Florivorous Fruit Flies (Diptera: Tephritidae) in Southern California.- 3.1 Introduction.- 3.2 Flora Analyzed.- 3.3 Tephritid Sampling and Rearing Procedures.- 3.4 Incidence of Florivorous Tephritidae Among Sampled Asteraceae.- 3.5 Tribal Affinities of Symphagous, Florivorous Tephritidae.- 3.6 Incidence and Coincidence of Genera of Symphagous Tephritidae Within Plant Tribes.- 3.7 Different Levels of Symphagy Among Southern California Tephritidae.- 3.8 Conclusions.- References.- 4 Establishment of Urophora cardui (Diptera: Tephritidae) on Canada Thistle, Cirsium arvense (Asteraceae), and Colony Development in Relation to Habitat and Parasitoids in Canada.- 4.1 Introduction.- 4.2 Life Cycle of Urophora cardui.- 4.3 Release Activities and Experimental Studies in Canada.- 4.3.1 Release Stock.- 4.3.2 Releases and Population Development in Saskatchewan.- 4.3.3 Habitat and Mortality in Saskatchewan.- 4.3.4 Recent Releases in British Columbia.- 4.3.5 Parasitism in Eastern Canada.- 4.4 Results.- 4.4.1 Release Stock.- 4.4.2 Releases and Population Development in Saskatchewan.- 4.4.3 Habitat and Mortality in Saskatchewan.- 4.4.4 Recent Releases in British Columbia.- 4.4.5 Parasitism in Eastern Canada.- 4.5 Discussion.- 4.5.1 Release Stock.- 4.5.2 Releases, Population Development and Habitat.- 4.5.3 Parasitism in Eastern Canada.- 4.6 Conclusions.- References.- B Host-Parasite Interactions.- 5 Host Relationships at Reversed Generation Times: Margaritifera (Bivalvia) and Salmonids.- 5.1 Introduction.- 5.2 The Three Margaritifera Species Sensu Stricto.- 5.3 Characteristics of the Host-Parasite Relationship.- 5.3.1 The Parasitic Stage.- 5.3.2 Host Range and Host Specificity.- 5.3.3 Relation Between the Generation Time of Parasite and Host.- 5.4 The Framework for the Evolution of the Host-Parasite Relationship.- 5.4.1 Condition 1: Mode of Host Infection and Parasitic Association.- 5.4.2 Condition 2: Mutual Impact.- 5.4.3 Condition 3: Phylogenetic History.- 5.4.4 Condition 4: Rates of Evolution.- 5.5 Evolutionary Mechanisms.- 5.5.1 Selective Pressure for a Host Range as Broad as Possible.- 5.5.2 Selective Pressure for a High Degree of Adaptation.- 5.6 Evolutionary Outcome.- References.- 6 The Community Structure of Ticks on Kudu, Tragelaphus strepsiceros, in the Eastern Cape Province of South Africa.- 6.1 Introduction.- 6.2 Methods and Materials.- 6.3 Results.- 6.4 Discussion.- References.- 7 The Epidemiology of Parasitic Diseases in Daphnia.- 7.1 Introduction.- 7.1.1 Parasites in Zooplankton Populations.- 7.2 The Abundance of Daphnia Microparasites in Natural Populations.- 7.3 The Biology of Transmission in Aquatic Systems.- 7.3.1 Waterborne Transmission.- 7.3.2 Survival of Transmission Stages Outside the Host.- 7.4 The Spread of Microparasites.- 7.4.1 Parasite Transmission Is Density Dependent.- 7.4.2 Parasite Transmission Can Be Limited by Low Temperatures.- 7.4.3 Host Stress Might Facilitate Parasite Spread.- 7.5 Epidemiology of Daphnia Microparasites.- 7.5.1 A Mechanism for Invasion, Spread and Decline of Parasites in Cladocerans.- 7.5.2 A Mathematical Model for the Epidemiology of Plankton Parasites.- 7.5.3 Analysis of the Model.- 7.6 Discussion.- References.- C Aspects of Chemical Ecology in Different Food Chains.- 8 Inter- and Intraspecific Transfer of Toxic Insect Compound Cantharidin.- 8.1 Introduction.- 8.2 Toxic Cantharidin: Biological Activity, Mode of Action, Occurrence and Ecological Significance.- 8.3 Attractivity and Significance of Natural and Synthetic Cantharidin to Canthariphilous Insects.- 8.4 Transfer of Cantharidin Through Developmental Stages and Between Individuals in Canthariphilous Species.- 8.5 Interspecific Transfer of Cantharidin.- 8.5.1 From Producers and Canthariphiles to Cantharidin-Tolerant and Nontolerant Predators.- 8.5.2 From Producers to Canthariphiles and Within Canthariphiles.- 8.6 Evolution of Canthariphily.- 8.6.1 Cantharidin May Increase Individual Fitness.- 8.6.2 Detoxication of Cantharidin in Producers, Canthariphilous Insects and Cantharidin-Tolerant Animals.- 8.6.3 Evolution of Attractancy of Toxic Cantharidin in Canthariphilous Insects.- 8.6.4 Evolution of Cantharidin Transfer Through Trophic Levels.- References.- 9 Survival in a Hostile Environment. Evaluation of the Developmental Success of the Oligophagous Leaf Beetle Chrysomela vigintipunctata (Scop).- 9.1 Introduction.- 9.2 Chemical Defence in Adults and Larvae.- 9.3 Feeding Preference and Oviposition. Not All Mothers Know Best.- 9.4 Fecundity.- 9.5 Feeding Performance of Larvae and Developmental Rates.- 9.6 Impact of Predators and Parasitoids.- 9.7 Pre-diapause Feeding of Adults and Induction of Diapause.-…