Food Webs

by

Mary I. O'Connor, Joanna R. Bernhardt, Natalie C. Caulk

• LAST REVIEWED: 29 June 2015
• LAST MODIFIED: 29 June 2015
• DOI: 10.1093/obo/9780199830060-0138

Introduction

The food web is a network description of energy, species, and individuals in communities and ecosystems according to feeding relationships between interacting species. Food webs integrate an understanding of individual performance and physiological conditions with higher-order processes of energy flow and standing stocks, thus uniting community and ecosystem ecology. Despite the importance of this concept, there has not been a single, central theory or set of methods for studying food webs; thus the discipline has multiple facets and methods, ranging widely from empirical and energetic studies to dynamic mathematical theory to highly sophisticated network analyses. Early empirical studies, beginning in the late 19th century but flourishing in the 1970s through 1990s, documented feeding relationships among species in aquatic and terrestrial ecosystems, and created networks to represent these systems. Analyses of these data, and independent theoretical work, suggested that food webs shared certain properties across all systems that conferred an understanding of community stability or function based on the number of species in a food web, the number of links between species, or the strength of interactions between species. More recent work has sought to determine whether the patterns in and significance of food web structure for ecosystem function are artifacts of data collection methods, or if they represent biological reality. Major themes include investigations into the relationship between the diversity of species (or complexity) of a food web network and its stability, estimation of the distribution of the strength or importance of feeding relationships (interaction strengths), and the use of body size to predict structure, approximate feeding relationships, and the strength of feeding links. An emphasis on body size as a determinant of biological processes within food webs, or as a proxy for estimating feeding relationships, emerges in almost every aspect of the food web literature. Another major and relatively recent theme (since the late 1980s) in the study of food webs is the role of scale (spatial, temporal, and biological). The canon of food web literature has identified major patterns in food webs and the processes that underlie them, regardless of the particulars of the species or ecosystem in question. The vast majority of food web studies, however, have applied food web concepts to understand or document local ecosystems and to consider how environmental change (biodiversity loss, climate change, overfishing) will affect the function of natural communities and ecosystems based on a model of ecosystems as trophic networks.

General Overviews

Elton 1927 is credited with the development, if not introduction, of the food web concept in the author’s writings of observations of repeatable patterns in nature of complex relationships among animal species through their feeding relationships. This initial overview of food web ecology emphasizes pattern and observation in the field, and comparisons across ecosystems. However, the historical overview Dunne 2012 suggests that the ecological importance of food webs predates Elton’s publication by over 30 years. Dunne 2012 identifies three phases of developments in the study of food webs: an early phase characterized by observation and insight, a middle phase seeking to analyze and compare abstracted properties to understand ecological systems, and a contemporary phase with approaches enhanced by more datasets and computing power to support newer thinking of food webs as networks. Polis, et al. 2004 provides an alternative and thorough overview of the evolution of the food web concept that extends from the view that webs are limited to local communities to the one where they integrate communities and ecosystems across habitats. Pascual and Dunne 2006 views food webs as networks and how they relate to dynamics in food webs, emphasizing species diversity. Somewhat distinct from these approaches is the view of food webs as energetic systems. Belgrano, et al. 2006 includes several empirical perspectives on food webs, from both energetic and network backgrounds; it also considers food webs in model systems (e.g., experimental aquaria) and in natural, field systems. McCann 2012 provides a conceptually accessible and mathematically sophisticated integration of theoretical and empirical work on food webs from population dynamics through food web modules, considering as well the ecosystem consequences of food web. McCann 2012 and Belgrano, et al. 2006 effectively consider both dynamic and energetic views of food webs. McCann 2000 is a concise yet thorough overview of the long-running interest in how food web structure and complexity affect their stability.

• Belgrano, A., U. M. Scharler, J. Dunne, and R. E. Ulanowicz. 2006. Aquatic food webs: An ecosystem approach. Oxford: Oxford Univ. Press.

  An edited volume that synthesizes theory, methods, and empirical data to understand the dynamical nature of food webs in an ecosystem context. Although the data to illustrate the arguments is drawn from aquatic ecosystems, the material and concepts are general and readily apply to any food web thinking and application.

• Dunne, J. A. 2012. Food webs. In Computational complexity theory, techniques and applications. Edited by Robert A. Myers, 1155–1176. New York: Springer-Verlag.

  A comprehensive review of food webs studied as networks and the ecological insights gained from this study. The chapter includes over 111 citations to published articles as well as a bibliography of books and reviews.

• Elton, C. S. 1927. Animal ecology. New York: Macmillan.

  Classic text outlining general ecological principles, including food chains, food size, and the pyramid of numbers (Eltonian pyramid) as a representation of ecosystems in terms of feeding relationships. One of the seminal works that defined the field of ecology.

• McCann, K. S. 2000. The diversity-stability debate. Nature 405:228–233.

  DOI: 10.1038/35012234

  McCann concisely reviews high points of one major theme in food web research: the debate about whether increased diversity in food webs increases or decreases system stability. The article briefly summarizes classic thinking on the issue and more deeply analyzes contemporary work and its implications for consequences of biodiversity loss.

• McCann, K. S. 2012. Food Webs. Monographs in population biology. Princeton, NJ: Princeton Univ. Press.

  A recent and comprehensive synthesis of how interaction strengths affect food web structure and dynamics. It is a conceptual synthesis with mathematical framing and evidence, also integrating some empirical data. The book formally scales up from pairwise species interactions through coupled habitats to ecosystem level food web processes.

• Pascual, M., and J. A. Dunne. 2006. Ecological networks: Linking structure to dynamics in food webs. New York: Oxford Univ. Press.

  This edited volume provides reviews of topics related to diversity and complexity in food webs, and several chapters relate food webs to other problems in community ecology including coexistence, habitat loss, and biodiversity loss. The introduction includes a bibliography of general food web books and reviews (p. 16).

• Polis, G., M. E. Power, and G. E. Huxel. 2004. Food webs at the landscape level. Chicago: Univ. of Chicago Press.

  This edited volume provides foundations for understanding food webs as systems of fluxing energy and materials, as well as how food webs occur across ecosystem boundaries. With particular emphasis on terrestrial-aquatic boundaries, chapters provide theory and data to explore how the biological networks of food webs link ecosystems across space.