What is rarity?

Abstract

Population and community biology have repeatedly been plagued with problems of definition. The meaning of such fundamental terms and concepts as competition, density dependence, carrying capacity, niche, stability and community have all, and often for prolonged periods, been debated (e.g. Pimm, 1984; Giller and Gee, 1987; Murray, 1987; Dhondt, 1988; Keddy, 1989; Schoener, 1989). Such discussion of the use and interpretation both of words and concepts may, on occasion, degenerate into arguments over semantics. However, for any area of study, clarity of terminology is essential to the establishment of a rigorous framework in which both theoretical and empirical work can be placed. With regard to the study of rarity no general theory and no such framework presently exist. At the outset, therefore, we would do well to be clear about what we mean by rarity and rare species.

Discussions will soon be at cross-purposes if it is not clearly recognised that our concepts of what is rare will depend on the scale of our individual experience and on the range or narrowness of our special interests. J. L. Harper (1981)

Rarity is one of those concepts that suffuses our culture: it defies precise definition and when used by the scientist it is often given a spurious accuracy to satisfy our need for precision. V. H. Heywood(1988)