Food Webs

Abstract

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 (Based on field observations of feeding by each species, O.J. Schmitz, unpublished data.)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.

close

References

Beckerman AP, Petchey OL and Warren PH (2006) Foraging biology predicts food web complexity. Proceedings of the National Academy of Sciences of the USA 103: 13745–13749.

Dunne JA (2006) The network structure of food webs. In: Pascual M and Dunne JA (eds) Ecological Networks: Linking Structure to Dynamics in Food Webs, pp. 27–86. Oxford, UK: Oxford University Press.

Martinez ND (1995) Unifying ecological subdisciplines with ecosystem food webs. In: Jones C and Lawton J (eds) Linking Species and Ecosystems, pp. 166–176. New York: Chapman & Hall.

McCann KS (2000) The diversity‐stability debate. Nature 405: 228–233.

Pimm SL, Lawton JH and Cohen JE (1991) Food web patterns and their consequences. Nature 350: 669–674.

Post DM (2002) The long and short of food chain length. Trends in Ecology and Evolution 17: 269–277.

Schmitz OJ, Krivan V and Ovadia O (2004) Trophic cascades: the primacy of trait‐mediated indirect interactions. Ecology Letters 7: 153–163.

Schoener TW (1989) Food webs from the small to the large. Ecology 70: 1559–1589.

Williams RJ, Berlow EL, Dunne JA, Barabási A‐L and Martinez ND (2002) Two degrees of separation in complex food webs. Proceedings of the National Academy of Sciences of the USA 99: 12913–12916.

Williams RJ and Martinez ND (2000) Simple rules yield complex food webs. Nature 404: 180–183.

Wootton JT and Emmerson M (2005) Measurement of interaction strength in nature. Annual Review of Ecology, Evolution and Systematics 36: 419–444.

Further Reading

Cohen JE, Briand F and Newman CM (1990) Community Food Webs: Data and Theory. New York: Springer.

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.

Pimm SL (1991) The Balance of Nature? Chicago, IL: University of Chicago Press.

Polis GA, Power ME and Huxel GR (2004) Food Webs at the Landscape Level. Chicago, IL: University of Chicago Press.

Polis GA and Winemiller K (1995) Food Webs: Integration of Pattern and Dynamics. New York: Chapman & Hall.

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.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

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]