Intraspecific competition
A male Blackbird (Turdus merula) singing. Bird song often functions as a signal in territory defense. (By Malene Thyssen, http://commons.wikimedia.org/wiki/User:Malene)
Published: January 17, 2008, 6:20 pm
Updated: March 28, 2013, 5:33 pm
This article has been reviewed by the following Topic Editor:
Kevin J. Caley
Intraspecific competition is the conflict over resources between members of the same species. Individuals may compete over mates, water, sunlight, territory or food energy sources. Intraspecific competition is an important factor limiting the population size of many species.
Intraspecific population regulation
Competition among individuals of the bunchgrass Hilaria rigida (big galleta grass) results in an even spatial dispersion of individuals. (Photo by R. Robberecht)
If members of the same species are competing for limited resources, then each individual would receive fewer resources when the population size of intraspecific competitors increases. Fewer resources per individual will (1) decrease the growth rates of individuals, (2) increase the chance that individuals die of starvation, or (3) decrease the number of offspring that a female can produce. Thus, as population density increases, there will be a resultant decrease in population growth rate. Intraspecific competition can cause populations to stop growing when they reach their carrying capacity (see logistic growth).
Intraspecific competition and patterns of spatial dispersion
Intraspecific competition can influence the spatial dispersion of organisms in a population. For example, if plants are competing for soil resources, there may be a limit to how close together individual plants of the same species can live. Thus, intraspecific competition can result in plants having an even pattern of distribution across the environment.
Limiting the effects of intraspecific competition
Individuals may try to limit competition for resources by defending limited resources from use by other members of their species. The physical defense of resources from other members of the same species is an example of interference competition. In some cases animals may defend territories to allow them to have exclusive use of the resources in the territory. Animals may defend territories to provide them with access to food or other resources or to provide them with a space where they can safely raise their young. Males of many species defend territories from other males of their own species for exclusive access rights to mating with the females living in their territory.
Further reading
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Campbell, N.A., J.B. Reece, and L.G. Mitchhell. 2006. Biology. Addison Wesley Longman, Inc. Menlo Park, CA. ISBN: 080537146X
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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
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Citation
Mark McGinley (Lead Author);Mark McGinley (Contributing Author);Kevin J. Caley (Topic Editor) "Intraspecific competition". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth January 17, 2008; Last revised Date March 28, 2013; Retrieved June 19, 2013 <http://www.eoearth.org/article/Intraspecific_competition>
The Author
Mark McGinley is an Associate Professor in the Honors College and Department of Biological Sciences at Texas Tech University. He has conducted research in the evolutionary, behavioral, and community ecology of animals and plants. Dr. McGinley’s recent scholarly interests focus on educating the general public about scientific (particularly environmental) issues. He is currently working closely with students in an interdisciplinary degree program, Natural History and Humanities, which combine ... (Full Bio)
Intraspecific competition is the conflict over resources between members of the same species. Individuals may compete over mates, water, sunlight, territory or food energy sources. Intraspecific competition is an important factor limiting the population size of many species.
Intraspecific population regulation
Competition among individuals of the bunchgrass Hilaria rigida (big galleta grass) results in an even spatial dispersion of individuals. (Photo by R. Robberecht)
If members of the same species are competing for limited resources, then each individual would receive fewer resources when the population size of intraspecific competitors increases. Fewer resources per individual will (1) decrease the growth rates of individuals, (2) increase the chance that individuals die of starvation, or (3) decrease the number of offspring that a female can produce. Thus, as population density increases, there will be a resultant decrease in population growth rate. Intraspecific competition can cause populations to stop growing when they reach their carrying capacity (see logistic growth).
Intraspecific competition and patterns of spatial dispersion
Intraspecific competition can influence the spatial dispersion of organisms in a population. For example, if plants are competing for soil resources, there may be a limit to how close together individual plants of the same species can live. Thus, intraspecific competition can result in plants having an even pattern of distribution across the environment.
Limiting the effects of intraspecific competition
Individuals may try to limit competition for resources by defending limited resources from use by other members of their species. The physical defense of resources from other members of the same species is an example of interference competition. In some cases animals may defend territories to allow them to have exclusive use of the resources in the territory. Animals may defend territories to provide them with access to food or other resources or to provide them with a space where they can safely raise their young. Males of many species defend territories from other males of their own species for exclusive access rights to mating with the females living in their territory.
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
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Tiger marking territory. (Photo from Save the Tiger Fund)
1 Comment
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