Dynamic Food Webs

Multispecies Assemblages, Ecosystem Development and Environmental Change

Peter C de Ruiter, Volkmar Wolters, John C Moore

• Publisher: Academic Press
• Year: 2005
• eBook ISBN: 9780080460949
• Topic: Biological Sciences
• Subtopic: Ecology
• Index: Biological Sciences

Dynamic Food Webs challenges us to rethink what factors may determine ecological and evolutionary pathways of food web development. It touches upon the intriguing idea that trophic interactions drive patterns and dynamics at different levels of biological organization: dynamics in species composition, dynamics in population life-history parameters and abundances, and dynamics in individual growth, size and behavior. These dynamics are shown to be strongly interrelated governing food web structure and stability and the role of populations and communities play in ecosystem functioning.Dynamic Food Webs not only offers over 100 illustrations, but also contains 8 riveting sections devoted to an understanding of how to manage the effects of environmental change, the protection of biological diversity and the sustainable use of natural resources.Dynamic Food Webs is a volume in the Theoretical Ecology series.- Relates dynamics on different levels of biological organization: individuals, populations, and communities- Deals with empirical and theoretical approaches- Discusses the role of community food webs in ecosystem functioning- Proposes methods to assess the effects of environmental change on the structure of biological communities and ecosystem functioning- Offers an analyses of the relationship between complexity and stability in food webs

Section 1

Introduction

Outline

1.0: TRIBUTE

1.1: DYNAMIC FOOD WEBS

1.2: FOOD WEB SCIENCE: Moving on the path from abstraction to prediction

1.0

TRIBUTE

Kevin McCann, Mariano Koen-Alonso, Alan Hastings and John C. Moore

In the time since the last symposium held at Pinagree Park, ecology lost two formidable and important ecologists in Gary Polis and Peter Yodzis. Their presence was sorely missed at the most recent food web conference in Giessen, Germany, as their passion and enthusiasm for ecology served as a catalyst at any gathering. In the area of food web ecology, they are figures of major historical importance, both scientists continuously pushing and challenging the boundaries of our understanding. In this manner they were very similar. Gary and Peter were inspired by the beauty and complexity of the world around them, and both men were fearless in their attempts to begin to understand one of nature’s most complicated puzzles, the food web. Additionally, both men were powerful personalities and determined to forge their own path in the history books of ecology. In other ways it would be hard to find two men so completely different. Gary Polis was a scorpion expert, and a hardcore empirical ecologist; Peter Yodzis was a theoretical physicist specializing in general relativity before becoming an ecologist. Gary brought unbridled amounts of enthusiasm to the scientific table. In doing so he was able to inspire a new generation of ecologists to challenge old ideas. Gary was a champion of field observation and the manipulative experiment. His work more than once reminded us of the complexity of nature, the oversimplifications behind our assumptions, and the power of reason by counterexample. Peter, on the other hand, championed the development of ecological theory that was founded on the clear and rigorous tools of the physicist. He loved thought experiments (the Gedanken experiments of Einstein). To him, the thought experiment distilled the essentials of a good scientist by forcing the scientist to pose a problem that was both clear and answerable upon logic alone. This is not to say that he believed the thought experiment as an end but rather saw it as a creative way of developing one of the most important tools of the scientist—intuition. In a historical sense, their differences represent the two aspects of ecology (theory and empiricism); however, here, too, they played an important role in bringing theory to empiricism and empiricism to theory. As one can see from this book, their efforts permeate all recent advances in food web ecology.

At a personal level, both men were deeply compassionate and caring toward family and friends. Again they did this in slightly different ways. Gary Polis’s magnetic character and joie de vie warmed and engaged all those around him. From Peter Yodzis emanated an enormous warmth and gentle concern for all those lucky enough to come into his circle. They will be deeply missed as scientist and friends.

1.1

DYNAMIC FOOD WEBS

Peter C. de Ruiter, Volkmar Wolters and John C. Moore

Publisher Summary

Food webs are special descriptions of biological communities focusing on trophic interactions between consumers and resources. They have become a central issue in population, community, and ecosystem ecology. They provide a way to analyze the interrelationships among community dynamics and stability and ecosystem functioning, and how these are influenced by environmental change and disturbance. Population dynamics of interacting predators and prey are difficult to predict, and many ecosystems are known to contain hundreds or thousands of these interactions arranged in highly complex networks of direct and indirect interactions. Approaching food web structure and dynamics from environmental characteristics shows that environmental heterogeneity may create subsystems, especially at the lower trophic levels in food webs, with organisms at the higher trophic levels that act as “integrators” across this variability in space and time and stabilize dynamics of their resources via density-dependent adaptive foraging. Approaching food web structure from dynamics in populations shows that the evolution of realistic food web structures can be explained on the basis of simple rules regarding population abundance and species occurrence. The analyses of biological properties of individuals within populations show a strong explanatory power of body size to population abundance scaling rules in understanding the dynamics and persistence of trophic groups in food webs. Resource availability and use may govern the structure and functioning of food webs; in turn, food web interactions are the basis of ecosystem processes and govern important pathways in the global cycling of matter, energy, and nutrients.

MULTISPECIES ASSEMBLAGES, ECOSYSTEM DEVELOPMENT, AND ENVIRONMENTAL CHANGE

One of the most intensively studied food webs in ecological literature is that of Tuesday Lake in Michigan (USA) (Jonsson et al., 2004). The species composition in this food web was observed in two consecutive years, 1984 and 1986, while in between three planktivorous fish species were removed and one piscivorous fish species was added. This manipulation had hardly any effect on species richness (56 in 1984, 57 in 1986), but remarkably changed species composition as about 50% of the species were replaced by new incoming species. Manipulating one species and seeing effects on dozens of species reveals the importance of species interactions. It shows that species come and species go, populations fluctuate in numbers, and individuals grow and in connection with this may alter in the way they interact with other species. It shows the open, flexible, and dynamic nature of food webs.

Food webs are special descriptions of biological communities focusing on trophic interactions between consumers and resources. Food webs have become a central issue in population, community, and ecosystem ecology. The interactions within food webs are thought to influence the dynamics and persistence of many populations in fundamental ways through the availability of resources (i.e., energy/nutrients) and the mortality due to predation. Moreover, food web structure and ecosystem processes, such as the cycling of energy and nutrients, are deeply interrelated in that the trophic interactions represent transfer rates of energy and matter. Food webs therefore provide a way to analyze the interrelationships between community dynamics and stability and ecosystem functioning and how these are influenced by environmental change and disturbance.

Naturalists long ago observed how the distribution, abundance, and behavior of organisms are influenced by interactions with other species. Population dynamics of interacting predators and prey are difficult to predict, and many ecosystems are known to contain hundreds or thousands of these interactions arranged in highly complex networks of direct and indirect interactions. Motivated in part by May’s (1972) theoretical study of the complexity-stability relationship, the study of food webs gained momentum in the late 1970s and early 1980s (Cohen, 1978; Pimm, 1982). A formal means of dealing with the flow of energy and matter in food webs was ushered with the advent of ecosystem ecology (Odum, 1963), and since then the food web approach has been adopted to analyze interrelationships between community structure, stability, and ecosystem processes (DeAngelis, 1992).

The first food web symposium was convened at Gatlinburg, North Carolina, in 1982 (DeAngelis et al., 1982). That symposium was dominated by theoretical studies focused on the complexity-stability relationship and empirical studies examining features of simple topological webs (ball and stick diagrams) compiled from the published literature. The ensuing decade was marked by exploration of a greater number of issues influencing the structure and dynamics of food webs (interaction strength, indirect effects, keystone species, spatial variation, and temporal variation in abiotic drivers) and a search for more detailed and accurate food web descriptions. Some ecologists questioned the utility of analyzing features of web diagrams that quite obviously contained too few taxa, grossly unequal levels of species aggregation, and feeding links with no magnitudes or spatio-temporal variation (Hall and Raffaelli, 1997).

A second food web symposium, held at Pingree Park, Colorado, in 1993 (Polis and Winemiller, 1996), emphasized dynamic predator-prey models, causes and effects of spatial and temporal variation, life history strategies, top-down and bottom-up processes, and comparisons of aquatic, terrestrial, and soil webs. Over the last decade the ecological debate became increasingly dominated by a number of new topics, such as environmental change, spatial ecology, and functional implications of biodiversity. This has changed our view on the entities, scales, and processes that have to be addressed by ecological research, and the food web approach became recognized as a most powerful tool to approach these issues. This was the point-of-departure for the third food web symposium held in November 2003 in Schloss Rauischolzhausen, Germany. This volume presents the proceedings of this symposium.

Much more than its predecessors, this symposium highlights approaches to understand the structure and functioning of food webs on the basis of detailed analyses of biological properties of individuals, populations, and compartments within communities. Much emphasis is laid on the understanding of food web structure and stability. Some contributions approach food web structure and dynamics from ‘outside’ environmental variability, in space as well as in time. Other contributions take the opposite approach by looking in depth to the dynamics of populations and biological attributes of individual within populations.

Approaching food web structure and dynamics from environmental characteristics (Section 2) shows that environmental heterogeneity may create subsystems (compartments), especially at the lower trophic levels in food webs, with organisms at the higher trophic levels that act as ‘integrators’ across this variability in space and time and stabilize dynamics of their resources via density-dependent adaptive foraging. Such compartmentation has been observed at the level of spatial and temporal variation of resource availability; an example is provided for soil food webs, for which records of spatial and temporal variation indicate the primary energy source of soil organic matter as major driving force, with important implications for system stability (Moore and de Ruiter, 1997). This explicitly relates to MacArthur’s idea (MacArthur, 1955) that community complexity should buffer against perturbations, and thereby override inherent constraints on system stability imposed by complexity (May, 1972). Another aspect of environmental variability regards the dynamics in nutrient availability governing the interplay between competition and trophic interactions and by this the dynamics of the populations at various trophic levels. Comparison of food web structures from different habitats, soil, terrestrial and aquatic, shows regular patterns in the flows with which food is transferred and processed by the trophic groups in the food webs. This approach bridged the gap between looking at descriptive properties of food web structure, such as species richness and trophic levels and looking at species composition in detail, as it reveals regularities in food web structure that are crucial to food web stability and functioning and appears less sensitive to the dynamics in species composition in food webs.

Approaching food web structure from dynamics in populations (Section 3) shows that the evolution of realistic food web structures can be explained on the basis of simple rules regarding population abundance and species occurrence. Life-history–based dynamics within populations may even influence community dynamics in extraordinary and counterintuitive ways in the way that predators promote each other’s persistence when they forage on d...

Table of contents

• Cover image
• Title page
• Table of Contents
• CONTRIBUTORS
• Section 1: Introduction
• Section 2: Dynamic Food Web Structures
• Section 3: Population Dynamics and Food Webs
• Section 4: Body Size and Food Webs
• Section 5: Nutrient and Resource Dynamics and Food Webs
• Section 6: Biodiversity and Food Web Structure and Function
• Section 7: Environmental Change, Perturbations, and Food Webs
• Section 8: Thematic Reviews
• REFERENCES
• Keywords
• INDEX