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Estimating species numbers by extrapolation : a cautionary note

Ulrich W.

Polish Journal of Ecology

2001

Vol. 49, nr 3

299-305

This paper evaluates the accuracy any estimator of species may achieve if only a limited fraction (up to 3/4) of the species number in the community has been sampled. From the impossibility to infer the relative abundance distribution (RAD) the rare and not sampled species follow it is shown that it is only possible to give a lower and an upper boundary of the species number. The lower boundary may be inferred either from a fit of a log-normal type RAD or by a graphical method. In the latter case, the lower boundary is S[min]=(ln(d[min]-2icpt) / slope with d[min] being the minimal possible relative density in the community and icpt and slope being the intercept and the slope of the geometric series fitted through the linear part of the log-normal distribution. The upper boundary is found through an extrapolation of this geometric series up to d[min][S[max]=(ln(d[min])-icpt)/slope]. For any estimator to work d[min] has to be known.