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Rarefaction is a statistical technique useful in both pollution and evolutionary ecology. It can be used to infer whether samples are drawn from the same community and also to estimate minimum feasible sample size. In this setting it essentially tells the investigator what would have been found had sample size been smaller, but some surprising uses arise if questions are phrased properly. Rarefaction is most powerful in pollution ecology when entire curves, and not just single values, are calculated. In evolutionary ecology, species/genus and related ratios have been examined as an indicator of both competition and adaptive radiation, but rarefaction demonstrates that the former, at least, is rarely evidenced by such ratios. The ratios are largely determined by the number of species, and claimed relationships between the ratios and area are primarily artifacts of the high correlation between the ratios and species number. The analytic expressions for expectation and variance in rarefied samples and a FORTRAN IV program for their calculation are given.
ecology, diversity, environments, hierarchical distribution, rarefaction, species-abundance curve
Associate professor, Florida State University, Tallahassee, Fla