Excessive Assignment of Species Rank

Abstract

“There is, however, a systematic category which, in contrast to others, has withstood the changes in the nomenclature with a singular tenacity. This is the category of species. To be sure, some of the species described by Linnaeus have been split into two or more new ones, and yet a majority of the Linnaean species are still treated as species, not as subgenera, genera, or anything else. In animal and plant groups which are taxonomically well understood, and excepting the so-called ‘difficult’ ones (which constitute a special problem to be discussed below), the delimitation of species usually is subject to no dispute at all (May, 1940). To be sure, a few taxonomists have from time to time succumbed to the temptation of assigning the species rank to any local race distinct enough to permit every specimen to receive a determination label. Excesses of this sort were frequent, for example, among mammalogists and specialists on certain genera of butterflies, but a salutary reaction has apparently started against them. The notion, entertained by some biologists unfamiliar with the subject, that species are arbitrary units like all other systematic categories is unfounded. In fact, no category is arbitrary so long as its limits are made to coincide with those of the discontinuously varying arrays of living forms. The category of species has certain attributes peculiar to itself that restrict the freedom of its usage, and consequently make it methodologically more valuable than the rest.”