Article

Top-Down and Bottom-Up Regulation of Communities

Jonathan B. Shurin

in Ecology

ISBN: 9780199830060
Published online May 2012 | | DOI: http://dx.doi.org/10.1093/obo/9780199830060-0029
Top-Down and Bottom-Up Regulation of Communities

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  • Applied Ecology (Environmental Science)
  • Ecology and Conservation
  • Plant Ecology
  • Zoology and Animal Sciences

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The dichotomy between top-down and bottom-up forces acting on populations and communities has informed and motivated research in ecology over its entire history. Early practitioners emphasized the importance of bottom-up control because of the apparent association between many species and the supply of resources from the environment. Consumers and predators, the sources of top-down control, were often assumed to exert little influence over the composition of communities or the dynamics of ecosystems. Thomas Huxley’s famous assertion in 1883 that “all the great sea fisheries, are inexhaustible; that is to say, that nothing we do seriously affects the number of the fish” reflects the general impression about the effects of many consumers, including humans, on populations of their prey (“The abundance of the seas,” New York Times, 17 November 1895). Predators were considered to be agents of natural selection, removing unfit individuals but having little impact on the numbers of their prey, which were often thought to be capable of mounting effective defensive strategies and prodigious reproduction. Top-down regulation became a strong contender as an alternative to bottom-up control in the 1960s, when theoretical and empirical evidence began to accumulate that consumers exert considerable influence over the ecosystems they inhabit. Since then a much-richer picture has emerged of how, where, and when top-down and bottom-up forces come into play and of the interaction between the two. This article deals with approaches to disentangling the effects of predators and resources on communities and ecosystems and what they have revealed about the structure and dynamics of nature.

Article.  9736 words. 

Subjects: Applied Ecology (Environmental Science) ; Ecology and Conservation ; Plant Ecology ; Zoology and Animal Sciences

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