Interspecific Competition

Abstract

Interspecific competition is the mutual inhibition of growth rate among populations of different species that have common requirements for shared and limiting resources. Interspecific competition can be a potent force in adaptive evolution and, along with predation and herbivory, is a major factor shaping the structure and species diversity of biological communities.

Keywords: population growth; limiting resources; ecological niche; character displacement; coevolution

Figure 1.

Zero growth isoclines for competing species 1 (solid line) and 2 (dotted line) in the Lotka–Volterra model, plotted in a space defined by population numbers of the two species, N1 and N2. If N1 and N2 are such that the system lies to the right of both isoclines, then both N1 and N2 will tend to decrease (shown by thin solid and dotted arrows), resulting in the system moving in a direction indicated by the thick arrows. If the system lies to the left of both isoclines, then both N1 and N2 will tend to increase. If the system is to the right of the isocline for species 2, but to the left of the species 1 isocline, then N1 will increase, whereas N2 will decrease. The two isoclines in this example thus divide the relevant system space into three sections with different predicted trajectories.

Figure 2.

A graphical depiction of the dynamic consequences of different placements of zero growth isoclines in N1N2 space in the Lotka–Volterra model of two‐species competition. As in Figure , isoclines for species 1 and 2 are shown by solid and dotted lines, respectively. Arrows represent the system trajectories in different parts of the system space. Empty and solid circles represent unstable and stable equilibria, respectively. (a) The only stable equilibrium in this case is at N1 = r1/s11, N2 = 0, implying that whatever the initial relative abundance of the two species, species 1 will eventually drive species 2 to extinction. (b) The only stable equilibrium in this case is at N1 = 0, N2 = r2/s22, implying that species 2 will eventually drive species 1 to extinction. (c) In this case the system has a stable equilibrium at the intersection of the isoclines for the two species, and long‐term coexistence is, therefore, possible. Both equilibria representing the extinction of one or the other species are unstable. (d) In this case, the intersection of the isoclines is an unstable equilibrium, whereas both equilibria involving extinction of one of the species are stable. Which species eventually becomes extinct depends on the initial relative abundance of the two species (or where in the system space the trajectory starts).

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Further Reading

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Arthur W (1987) The Niche in Competition and Evolution. Chichester, UK: Wiley.

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Joshi A and Thompson JN (1996) Evolution of broad and specific competitive ability in novel versus familiar environments in Drosophila species. Evolution 50: 188–194.

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Yodzis P (1994) Predator prey theory and management of multispecies fisheries. Ecological Applications 4: 51–58.

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How to Cite close
Joshi, Amitabh(May 2001) Interspecific Competition. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003286]