The Community Concept

by

Mark Vellend

• LAST REVIEWED: 15 January 2019
• LAST MODIFIED: 23 May 2012
• DOI: 10.1093/obo/9780199830060-0011

Introduction

For almost as long as ecology has been a discipline, it has struggled to define what constitutes an ecological community. A sharp dichotomy emerged early on, contrasting the view that communities were tightly integrated entities consisting of interdependent species (the community-unit concept) vs. the view that species co-occur largely according to the individualistic response of each species to spatially variable environmental conditions (the individualistic concept). To a large degree, the latter view has dominated ecological thought since the mid-20th century, based to a considerable extent on empirical patterns of community composition along environmental gradients. However, it has been repeatedly pointed out that neither view (in its extreme form) can capture the reality of processes and patterns in real communities, in which species often show both some degree of interdependence and gradual change in composition based on environmental conditions. Despite the debate regarding the concept of an ecological community, the discipline of community ecology has thrived and remained a key pillar of the broader field of ecology, with intense debates over the importance of competition in driving community structure and the relative importance of processes occurring at different spatial and temporal scales, among others. Finally, while few contemporary theoretical ecologists treat communities as belonging to discrete types, the community-unit concept lives on in applied ecology, where the classification of communities (often described as “vegetation” or “ecosystem”) is commonplace in order to facilitate conservation management, prioritization, and policy.

Historical Background

Frederic Clements put forth the formal concept of a community as a coherent unit of study for ecologists. Clements considered the different species in a community as being tightly integrated and interdependent, much like the organs that make up a plant or animal, leading him to use the metaphor of the community as a “complex organism” (Clements 1916). Forbes 1887 articulated a similar view of the species living together in lakes. The community-unit view was challenged by Leonty Ramensky (see McIntosh 1983) and Henry Gleason (Gleason 1926), who argued that species respond individualistically to environmental factors, such that their distributions and abundances vary continuously from place to place, rather than forming discrete and internally integrated community types. Tansley 1935 is a sharp criticism of Clements’s views, especially his terminology. McIntosh 1985, Kingsland 1991, Kingsland 2005, and Kingsolver and Paine 1991 provide historical accounts of this debate and place it within the context of the development of ecology as a scientific discipline.

• Clements, Frederic E. 1916. Plant succession: An analysis of the development of vegetation. Washington, DC: Carnegie Institute of Washington Publication.

  DOI: 10.5962/bhl.title.56234

  A comprehensive account of Clements’s views on the nature of ecological communities, including the complex-organism metaphor and how perturbations from the “climax” state of a community are followed by a deterministic succession leading back to the original state.

• Forbes, Stephen A. 1887. The lake as a microcosm. Bulletin of the Illinois State Natural History Survey 15:537–550.

  A classic paper detailing the argument that species in a community are tightly integrated via their interactions with one another; the biota of lakes is used as a case study.

• Gleason, Henry A. 1926. The individualistic concept of the plant association. Bulletin of the Torrey Botanical Club 53:7–26.

  DOI: 10.2307/2479933

  Detailed articulation of the view that we are “treading upon rather-dangerous ground” in any attempt to define discrete plant associations. Clearly intended as a counterpoint to Clements 1916, although, oddly, without any explicit mention of Clements’ work (or any citations at all, apart from a few of Gleason’s earlier papers).

• Kingsland, Sharon E. 1991. Defining ecology as a science. In Foundations of ecology. Edited by Leslie A. Real and James H. Brown, 1–13. Chicago: Univ. of Chicago Press.

  A concise overview of some of the key foundational papers in ecology, including Clements 1916, Forbes 1887, and Gleason 1926. This and other chapters that introduce different sections of the book provide an excellent historical overview of ecology.

• Kingsland, Sharon E. 2005. The evolution of American ecology, 1890–2000. Baltimore: Johns Hopkins Univ. Press.

  A history of how ecology developed as a scientific discipline over the 20th century in the United States. A good complement to an earlier book, McIntosh 1985.

• Kingsolver, Joel G., and Robert T. Paine. 1991. Conversational biology and ecological debate. In Foundations of ecology. Edited by Leslie A. Real and James H. Brown, 309–317. Chicago: Univ. of Chicago Press.

  An overview of papers covering particularly contentious topics in ecology, including Tansley 1935, which the authors say “dismantled systematically” the most central idea in Clements 1916: the ecological community as a complex organism.

• McIntosh, Robert P. 1983. Excerpts from the work of L. G. Ramensky. Bulletin of the Ecological Society of America 64.1 (March): 7–12.

  English translations of excerpts from L. G. Ramensky, “Basic Regularities of Vegetation Cover and Their Study (on The Basis of Geobotanic Researches in Voronezh Province),” establishing the fact that Ramensky independently arrived at conclusions very similar to Gleason’s (see Gleason 1926). Available online for purchase or by subscription.

• McIntosh, Robert P. 1985. The background of ecology: Concept and theory. Cambridge, UK, and New York: Cambridge Univ. Press.

  DOI: 10.1017/CBO9780511608537

  An excellent book on the history of ecology, with an emphasis on the Anglo-American tradition.

• Tansley, Arthur G. 1935. The use and abuse of vegetational concepts and terms. Ecology 16:284–307.

  DOI: 10.2307/1930070

  A blunt and clearly articulated criticism of Clements’s ideas (see Clements 1916), signaling a general shift in the views of ecologists toward the individualistic concept.