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How do diverse species coexist in the complex networks of prey-predator interactions in nature? While most theoretical models predict that complex food webs do not persist, recent empirical studies have revealed the very complex structure of natural food webs. This discrepancy between theory and observation implies that essential factors stabilizing natural food webs are lacking from previous models. This chapter reviews these studies on food web complexity and its community-level consequences. It contends that the architectural flexibility arising from foraging adaptation of consumer species is key to explaining linkage patterns and persistent mechanisms of complex food webs. A novel hypothesis is presented, which relates the complexity-stability relationship to evolutionarily history of the community.

Studies on lakes provide some of the most complete investigations on the structure, dynamics, and energetics of food webs encompassing organisms from bacteria to vertebrates. The life cycle of organisms in temperate lakes is adapted to a highly seasonal environment. Food web interactions in these lakes depend on the seasonal overlap of the occurrence of potential prey, competitor, or predator species. This seasonal overlap (i.e., the match-mismatch of food web interactions) depends strongly on the seasonal dynamics of the physical environment of lakes, such as temperature, light availability, and mixing intensity. Consequently, climate variability influences food web interactions and hence the structure, dynamics, and energetics of lake food webs. This chapter provides examples and discusses the importance of seasonality for the understanding of various aspects of lake food webs and the impact of climate variability thereon.

This chapter presents size-based analyses of aquatic food webs, where body size rather than species identity is the principle descriptor of an individual's role in the food web, provides insights into food web structure and function that complement, and extends those from species-based analyses. Focus is given to body size because it underpins predator-prey interactions and dictates how the biological properties of individuals change with size. Thus, size-based food web analyses offer an approach for integrating community and ecosystem ecology with energetic and metabolic theory.

This chapter discusses adaptive diversification due to predator–prey interactions. It has long been recognized that consumption, that is, predation, can not only exert strong selection pressure on the consumer, but also on the consumed species. However, predation has traditionally received much less attention than competition as a cause for the origin and maintenance of diversity. By using adaptive dynamics theory as well as individual-based models, the chapter then illustrates that adaptive diversification in prey species due to frequency-dependent predator–prey interactions is a theoretically plausible scenario. It also describes conditions for diversification due to predator–prey interactions in classical Lotka–Volterra models, which requires analysis of coevolutionary dynamics between two interacting species, and hence of adaptive dynamics in two-dimensional phenotype spaces.

In order to appreciate fully the advantages of the inertial view of population growth, it is necessary to discuss some of the details of and debates about the predator-prey account of population cycles. This chapter argues that the ratio-dependant idealization of the predator-prey interaction is quite different from the more traditional prey-dependent idealization. Moreover, the former view is not conducive to cyclic behavior.

Although much of the attention to the trophic dynamics of communities is theoretical, empirical data on the different types of dynamics and the underlying mechanisms are increasingly reported. The dynamics of small food web modules, or simple webs, are compared with those of complex interactions. Food web modules are described as small systems that possess explicit dynamics. They can be seen as building blocks to construct more realistic food webs, which are subsets of the true complexity in trophic interactions in real ecosystems. It has been stated that in small food webs oscillating consumer-resource interactions occur in natural systems and that in chains of three or more levels trophic cascades seem to be important. Finally, new studies on the dynamics of complex interaction webs are mentioned, focusing on the consequences of specific patterning of interaction strengths across the web for the stability of the overall system.

Trinidadian guppies provided one of the first experimental demonstrations that predators have a significant impact on behaviour and morphology. This chapter begins with a brief general introduction to predator prey interactions. The consequences of variation in predation risk for Trinidadian guppies, and the trade-offs linked to effective predator defences are then evaluated. It asks if and when adaptive differences can be classed as evolutionary change, and considers the pitfalls associated with such assumptions. Schooling behaviour, evasive tactics, crypsis and colour patterns, mating activity, foraging, and time budgets are examined as well as the relationship between learning skills and geographic variation anti-predator responses. Age-related changes in morphology and behaviour are explored. The chapter ends by examining differences between the sexes in response to predation.

This chapter derives specific results for the bivariate logistic process in the contexts of competition, and predator-prey and epidemic processes. Here minor modifications to the transition rates cause substantial changes in the structure of stochastic realizations. Earlier discussions on cumulative size and power-law processes are woven into the discussion, and strong emphasis is placed on the development of computer simulation algorithms.

One way to address big-scale problems and processes is to use small-scale data to construct and test mechanistic models of events at higher levels of organization and at larger spatial scales. Even though this general approach to understanding ocean ecosystems underpins much of biological oceanography, it has not been so commonly used in efforts to understand the population and community dynamics of marine mammals. This chapter uses demographic and bioenergetic tools to explore difficult-to-observe predator-prey interactions in marine mammal communities. It aims to understand better the interactions of mammal-feeding killer whales with their prey species in the North Pacific region, particularly in the vicinity of the Aleutian archipelago.

Did the removal of megatons of upper-trophic-level consumers significantly alter food-web dynamics by removing significant levels of predatory controls over prey populations, removing an important prey resource for predator populations, and changing the sensitivity of the ecosystem to physical forcing because of new predator-prey functional relationships? In order to address this question, it is necessary to understand where and when whales were harvested in the North Pacific Ocean, and how this ultimately affected whale distribution. Whales were not uniformly distributed across this broad region, and the roles they played were concentrated in relatively small areas. This chapter shows where great whales formerly were found in abundance in the North Pacific, relates those distributions to oceanography, and briefly explores some examples of the magnitude of change that might have resulted from the loss of great whales in the Aleutian Islands and Bering Sea.

This introductory chapter discusses the development of the study of predator-prey interactions. It outlines some of the popular population models applied in the study of population dynamics and predation theory, starting with the Lotka-Volterra equation which is considered to be the standard predator-prey model of ecology. It then briefly looks into the Leslie matrix which supports the Lotka-Volterra equation. The chapter also briefly explains the authors' argument of viewing predator density or interference as a fundamental feature governing predator-prey interactions, an opinion that differs from most of the other proponents of population models.

This chapter follows the size-structure of the entire marine ecosystem. It shows how the Sheldon spectrum emerges from predator–prey interactions and the limitations that physics and physiology place on individual organisms. How predator–prey interactions and physiological limitations scale with body size are the central assumptions in size spectrum theory. To that end, this chapter first defines body size and size spectrum. Next, it shows how central aspects of individual physiology scale with size: metabolism, clearance rate, and prey size preference. On that basis, it is possible to derive a power-law representation of the size spectrum by considering a balance between the needs of an organism (its metabolism) and the encountered prey, which is determined by the spectrum, the clearance rate, and the size preference. Lastly, the chapter uses the solution of the size spectrum to derive the expected size scaling of predation mortality.

This chapter uses the community model to repeat many of the classic impact calculations of a single stock on the entire community. Here, a focus is the appearance of trophic cascades initiated by the removal of large predators. When a component of an ecosystem is perturbed, the effects are not isolated to the component itself but cascade through the ecosystem. Perturbations are mainly propagated through the predator–prey interactions. The chapter also considers the trade-offs between a forage fishery and a consumer fishery, and the extension of the maximum sustainable yield (MSY) concept to the community, before finally returning to the single-stock aspects.

Ecological communities consist of species that interact to varying degrees within the same geographical area, and so by definition exist within a landscape context. This chapter begins by reviewing the measures and different scales at which species diversity can be assayed, including the use of spatial partitioning to evaluate multiscale patterns of diversity. The chapter then reviews correlates of species diversity, including explanations for latitudinal and elevational diversity gradients, before considering how habitat loss and fragmentation are expected to influence species diversity. The chapter tackles the debate surrounding the relative importance of habitat amount versus fragmentation in predicting species’ responses to landscape change, and highlights the importance of studying these effects at a landscape rather than patch scale. The chapter concludes with a discussion of landscape effects on different types of species interactions, and how interactions among species in different communities can give rise to metacommunity structure and dynamics.

Interactions between species or groups of organisms, both cooperative and antagonistic, can be powerful generators of biological diversity. This chapter focuses on two key driving forces: arms races and coevolution. Predator–prey relationships provide clear examples of arms races, with predators having a range of general adaptations to capture prey, which have evolved varied defences. But there is little evidence for genuine coevolutionary responses in the sensory systems of the predators to better overcome prey defences. In contrast, coevolution seems widespread and diverse in brood and social parasites in birds and insects, and this has lead to extraordinary defences and counter adaptations in both parasite and host in a range of modalities.

This chapter begins with an outline of mathematical approaches for evaluating how genotypes/phenotypes might alter community structure, which points to predictions about when such effects should be strongest in nature. It then summarizes common approaches for empirical work, which might be broadly classed as (1) the effects of genotypes/phenotypes within and among populations, and (2) the year-by-year correspondence between phenotypic change and community change. These key questions examine the current state of knowledge for two classic applications of evolutionary thinking to community theory: predator–prey interactions and competition. The chapter also considers the importance of intraspecific genetic diversity for community structure, which echoes and extends the intense interest surrounding the effects of interspecific diversity.

Hundreds of plant and animal species co-exist in marine ecosystems. More than 150 years ago, Charles Darwin recognised explicitly the importance of species interactions by invoking the concept of a ‘tangled bank’ of species. These interactions play an important role in the maintenance of ecological stability in the face of natural and anthropogenic disturbances. However, the mechanisms underlying ecosystem stability in the face of environmental change remain poorly understood. This chapter examines the importance of body size, abundance, and food-web structure for ecosystem functioning. It considers the building blocks of food webs, body mass, species abundance, and predator-prey interactions, as well as the interrelationships between body mass and trophic position. It presents examples that are not restricted to marine ecosystems in order to understand the drivers and consequences of biodiversity change in a wide range of ecosystems. It also discusses the relevance of body mass to biodiversity-ecosystem function research.

This chapter introduces the concept of the consumer-resource link, the idea that each species in a community consumes resources and is itself consumed by other species. The consumer–resource link is the fundamental building block from which more-complex food chains and food webs are constructed. The chapter continues by exploring what is arguably the simplest consumer–resource interaction—one predator species feeding on one species of prey. Important topics discussed in the context of predator–prey interactions are the predator’s functional response, the Lotka–Volterra predator–prey model, the Rosenzweig–MacArthur predator–prey model, and the suppression-stability trade-off. Isocline analysis is introduced as a method for visualizing the outcome of species interactions at steady-state or equilibrium. Herbivory and parasitism are briefly discussed within the context of general predator–prey models.