Abundances and range sizes: measuring rarity

Abstract

The definitions of rarity outlined in the previous chapter are based on the relative magnitudes of species’ abundances or of their range sizes. There is, however, no such thing as the abundance or the range size of a species, even at a particular spatial and temporal scale. Rather, they are both generic terms, embracing several important distinctions. Answers depend on which groups of individuals are and are not included, and the methods by which abundance and range size are assessed.

I attempted to carry out the figures, which seem to behave according to some mathematical formula; but when I came to deal with 3/5 of an occurrence I decided it was profitless to go on! J. Grinnell(1922)

The concept of total areal geographic range, as one of the indissoluble characteristics of the taxonomic units species and subspecies, seems to be by no means adequately defined or understood in current zoological literature. K. P. Schmidt (1950)