Food Webs

Oswald J Schmitz, Yale University, New Haven, Connecticut, USA
Andrew P Beckerman, The University of Sheffield, Sheffield, UK

Published online: September 2007

DOI: 10.1002/9780470015902.a0003740

Food webs are a way of describing the lines of dependency among species in Nature. Such interdependencies are basic to all ecological processes in that species consume resources and are themselves consumed by their predators.

Keywords: complexity; connectance; feeding link; food chain; trophic interaction

Figure 1. Example food web diagram for a meadow ecosystem in northeastern Connecticut, USA. Arrows depict the feeding dependencies between species of plants and their herbivores and between species of herbivores and their carnivore predators. Plants from left to right are Kentucky blue grass (Poa pratensis), Timothy grass (Phleum pretense), clover (Trifolium repens), Cinquefoil (Potentilla simplex), rough-stemmed goldenrod(Solidago rugosa), tall goldenrod (Solidago altissima), Queen Anne's lace (Daucus carota) and milkweed (Asclepias syriaca). Herbivores, from left to right, are the leaf-chewing grass specialist grasshopper (Chorthippus curtipennis), and the generalist grasshopper (Melanoplus femurrubrum), and sap feeders including the specialist plant bug (Leptopterna dolobrata), the generalist spittle bug (Philaenus spumaris), the planthoppers (Stichtocephala festina and Campylenchia latipes) and the pentatomid (Acrosternum hilare) (below Stichtocephala), the plant bug (Lopidea media) and the specialist milkweed bug (Lygaeus kalmii). The hunting spiders from left to right are: the wolf spider (Rabidosa rabida), the nursery web spider (Pisaurina mira) and the jumping spider Phidippus rimator. (Based on field observations of feeding by each species, O.J. Schmitz, unpublished data.)
Figure 2. A stylized food web (left) depicting interconnections among different species. Different kinds of species are depicted by different symbols (i.e. diamonds, plants; circles, herbivores and squares, carnivores). The peculiar shading of each symbol depicts a unique species. Feeding links between two species are depicted by arrows, which also portray the direction of energy flow (i.e. from prey to predator). Order can be distilled by assigning species into trophic groupings (right) represented by rectangular boxes. Species within a box belong to the same trophic group with basal species in the lowest box, intermediate species in the middle box and top predator species in the upper box. Food web patterns are discerned by counting species within each box and the number of links between boxes.
Figure 3. Food web diagrams used to illustrate how complexity increases stability. In these stylized food webs, the composition of plant (diamonds), herbivore (circles) and carnivore (squares) species remains unchanged but the degree of interconnectedness between species varies. The systems range from low connectedness or low complexity as depicted in food web 1 to high connectedness or high complexity as depicted in food web 3.
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 References
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 Further Reading
    book Cohen JE, Briand F and Newman CM (1990) Community Food Webs: Data and Theory. New York: Springer.
    book DeAngelis DL (1992) Dynamics of Nutrient Cycling and Food Webs. New York: Chapman & Hall.
    Menge BA (1995) Indirect effects in marine rocky intertidal interaction webs: pattern and importance. Ecological Monographs 65: 21–74.
    Milo R, Itzkovitz S, Kashtan N et al. (2004) Superfamilies of evolved and designed networks. Science 303: 1538–1542.
    book Pimm SL (1991) The Balance of Nature? Chicago, IL: University of Chicago Press.
    book Polis GA, Power ME and Huxel GR (2004) Food Webs at the Landscape Level. Chicago, IL: University of Chicago Press.
    book Polis GA and Winemiller K (1995) Food Webs: Integration of Pattern and Dynamics. New York: Chapman & Hall.
    book Schmitz OJ (2007) Ecology and Ecosystem Conservation. Washington DC: Island Press.
    Warren PH (1990) Variation in food-web structure – the determinants of connectance. American Naturalist 136: 689–700.

Related Sub-Topics:

Herbivory, Predation and Parasitism | Food Webs
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Article Title: Food Webs
 
How to Cite close
Schmitz, Oswald J, and Beckerman, Andrew P(Sep 2007) Food Webs. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0003740]