Introduction

Interspecific competition occurs between members of two, or more, different species. Individuals may compete over a variety of limiting resources including food, water, light, soil resources, or space. Members of different species may compete by exploitative competition or by interference competition. Interspecific competition is an important factor limiting the population size of many species. In addition, interspecific competition can limit the number of species that can coexist in a community and affect the phenotypic characteristics of organisms in an attempt to reduce the effects of competition.

Interspecific competition and population regulation

Interspecific interference competition between lions and hyenas. (Photo by Anup and Manoj Shah)

Interspecific competition is an important factor limiting the population size of many species. The growth rate of a species will be limited as the population size of their competitors increases, either because they have access to fewer limiting resources (exploitative competition) or because of the negative effects of the direct interactions of their competitor (interference competition).

Interspecific competition and community structure

Interspecific competition can plan an important role in influencing aspects of community structure such as species richness, species diversity, and patterns of species abundance.

Species richness

Interspecific competition can limit the number of species that can coexist in a community. The competitive exclusion principle suggests that two species with exactly the same niche are not able to coexist.  Thus, when the niches of two competing species are too similar, one of the species will be driven to extinction or be extirpated from the range of the other (competitive exclusion).

Limiting the effects of interspecific competition

Species may respond to the effects of interspecific competition by evolving to fill slightly different niches (niche differentiation). The divergence in phenotype produced by natural selection to reduce the effects of competition are known as character displacement.

Models of interspecific competition

Ecologists have developed mathematical models to study interspecific competition. The Lotka-Volterra model of competition is a phenomenological model whereas Tilman's model of competition for resources is a mechanistic model that explicitly models the influence of exploitative competition between species.

Further reading

• Campbell, N.A., J.B. Reece, and L.G. Mitchhell. 2006. Biology. Addison Wesley Longman, Inc. Menlo Park, CA. ISBN: 080537146X
• Raven, P.H., G.B. Johnson, J.B. Losos, K.A. Mason, and S.R. Singer. 2008. Biology, 8th edition. McGraw Hill, New York, NY. ISBN: 0073227390