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Noncanonical Distributions of Commonness and Rarity
Author(s) -
Preston Frank W.
Publication year - 1980
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1937159
Subject(s) - sampling (signal processing) , log normal distribution , ecological niche , ecology , environmental niche modelling , genetic algorithm , biology , statistics , habitat , mathematics , physics , detector , optics
Some reported counts of species abundances, when tallied by octaves or other appropriate intervals, do not conform at all well to the expected normal (lognormal) distribution, but the departures therefrom seem to be by no means systematic or consistent. In the present paper we examine briefly two examples: The Audubon Christmas Bird Counts, and the counts of diatoms in freshwater streams. In some cases the departure may be due to defective, nonrandom, sampling; in others to using more than one method of sampling and then confounding the samples; in still others the sampling may be satisfactory, but the "universe" that is sampled may itself be a hybrid one, two universes (or more than two) interpenetrating one another. In the tropics the distribution of birds is lognormal but not canonical. Here the explanation must be different. The sigma values are far too low. I call these "congested" distributions. Biologically it may mean that there are more species than niches, a presumably unstable situation, possibly arising from recent (Pleistocene?) excessive speciation. Apparently some problems exist that deserve examination.