The Application of Island-biogeographic Theory to Forest Tracts: Problems in the Determination of Turnover Rates

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Any change in the species-composition of birds on ‘islands’ may be described potentially by a number of models, one of which is the equilibrium island biogeographic model. The proper application of the equilibrium model requires that several conditions be met; the most important of which are: (1) the ability to identify true ‘colonists’; (2) balanced immigration and extinction rates; and (3) no large-scale environmental alterations causing changes in species-composition between sampling intervals. Failure to meet such conditions may lead to improbable or unrealistic interpretations of species change within the context of equilibrium island biogeographic theory. This problem is illustrated with some recent data on birds residing in a small forest patch.

When the theory is used to determine the design characteristics of faunal reserves, the entire matter takes on added significance. Ecological justification for the preservation of large, contiguous areas cannot be gained from the equilibrium model. In addition, predictions of the model are virtually useless without an accompanying body of autecological information on the species intended to be preserved.

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Biological Conservation, v. 22, issue 3, p. 217-227