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island biogeography, theory of
island biogeography, theory of A theory, advanced in 1967 by R. H. MacArthur and E. O. Wilson and now shown to be too simplistic, so largely discredited, that the number of species on an island will reach a dynamic equilibrium between the continual immigration of species from a mainland source and the extinction of species already present. Once equilibrium is reached the species number will remain constant, but with a continually changing composition. The theory goes on to state that if the immigration rates and the extinction rates are known, then the species number at equilibrium can be calculated. They theory fails, however, to take account of species interaction or of habitat diversity which is, de facto, usually greater on big islands; it also makes a major and possibly erroneous assumption that immigration is independent of island size. The theory also compares topographically identical near and far islands in relation to the mainland source, maintaining that near islands would have a higher rate of immigration than far ones because the biogeographical barrier presented by the sea would be smaller. It also states that the extinction rate would be independent of island location, and therefore the resulting equilibrium point for the number of species would be higher for the nearer islands. The assumption that the extinction rate is independent of island location may be incorrect because of the rescue effect.
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MICHAEL ALLABY. "island biogeography, theory of." A Dictionary of Ecology. 2004. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "island biogeography, theory of." A Dictionary of Ecology. 2004. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O14-islandbiogeographytheoryf.html MICHAEL ALLABY. "island biogeography, theory of." A Dictionary of Ecology. 2004. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O14-islandbiogeographytheoryf.html |
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island biogeography, theory of
island biogeography, theory of A theory, advanced in 1967 by R. H. MacArthur and E. O. Wilson and now largely discredited, that the number of species on an island will reach a dynamic equilibrium between the continual immigration of species from a mainland source and the extinction of species already present. Once equilibrium is reached the species number will remain constant, but with a continually changing composition. The theory goes on to state that, if the immigration rates and the extinction rates are known, then the species number at equilibrium can be calculated. The theory fails, however, to take account of species interaction or of habitat diversity which is, de facto, usually greater on big islands; it also makes a major and possibly erroneous assumption that immigration is independent of island size. The theory also compares topographically identical near and far islands in relation to the mainland source, maintaining that near islands would have a higher rate of immigration than far ones because the biogeographical barrier presented by the sea would be smaller. It also states that the extinction rate would be independent of island location, and therefore the resulting equilibrium point for the number of species would be higher for the nearer island. The assumption that the extinction rate is independent of island location may be incorrect because of the rescue effect.
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Cite this article
MICHAEL ALLABY. "island biogeography, theory of." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "island biogeography, theory of." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O7-islandbiogeographytheoryf.html MICHAEL ALLABY. "island biogeography, theory of." A Dictionary of Plant Sciences. 1998. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O7-islandbiogeographytheoryf.html |
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island biogeography
island biogeography The study of the distribution of plant and animal species on islands or in areas that are sufficiently isolated to resemble islands. Islands are numerous and their biotas (see island biotas) are often small enough to be quantified. Accordingly it has been possible to determine a relationship between area and species number, postulated to be an equilibrium between immigration and extinction (see rescue effect; and island biogeography, theory of). This is the basis of island biogeography, and it may equally be applied on continents, where plant and animal communities are effectively reduced to islands in a sea of cultivation or urbanization.
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Cite this article
MICHAEL ALLABY. "island biogeography." A Dictionary of Ecology. 2004. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "island biogeography." A Dictionary of Ecology. 2004. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O14-islandbiogeography.html MICHAEL ALLABY. "island biogeography." A Dictionary of Ecology. 2004. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O14-islandbiogeography.html |
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island biogeography
island biogeography The study of the distribution of plant and animal species on islands or in areas that are sufficiently isolated to resemble islands. Islands are numerous, and their biotas (see ISLAND BIOTAS) are often small enough to be quantified. Accordingly it has been possible to determine a relationship between area and species number, as an equilibrium between immigration and extinction (see EQUILIBRIUM THEORY; RESCUE EFFECT). This is the basis of island biogeography, and it also has great relevance to the continents, where plant and animal communities are effectively reduced to islands in a sea of cultivation or urbanization.
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Cite this article
MICHAEL ALLABY. "island biogeography." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "island biogeography." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O7-islandbiogeography.html MICHAEL ALLABY. "island biogeography." A Dictionary of Plant Sciences. 1998. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O7-islandbiogeography.html |
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island biogeography
island biogeography Basically, the relationship between area and species number, as an equilibrium between immigration and extinction, on islands; a study that is possible because islands are numerous and their biotas are often small enough to be quantified. The subject also has great relevance to the continents, where plant and animal communities are effectively reduced to islands in a sea of cultivation or urbanization.
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Cite this article
MICHAEL ALLABY. "island biogeography." A Dictionary of Zoology. 1999. Encyclopedia.com. 28 May. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "island biogeography." A Dictionary of Zoology. 1999. Encyclopedia.com. (May 28, 2012). http://www.encyclopedia.com/doc/1O8-islandbiogeography.html MICHAEL ALLABY. "island biogeography." A Dictionary of Zoology. 1999. Retrieved May 28, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O8-islandbiogeography.html |
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