The Genus in Evolutionary Taxonomy

Abstract

THE idea of genus as smallest of plant or animal that can be recognised without close study was an extremely important one in earlier periods of taxonomy (Bartlett, 1940). The species was a subdivision of it, often requiring expert examination both before it could be recognised and before it could be named, since specific name was at once a qualification of generic name and a differentiation all other specific names within that genus. Hence custom of putting generic name first. More than a trace of this same attitude to genus can be seen in results of Anderson's minor census (1940) of botanical opinion, which revealed a high proportion in favour of view that genus is more natural than species. It is presumably extreme usefulness of genus taken in this sense that leads Just (1953) to affirm that from a purely systematic point of view, genus still comprises [sic] most effective taxonomic unit on which new classifications of higher groups can be based. . Linnaeus seems to me to stand halfway between this earlier practice and more modern ones. For naming, he retains older ideas and states emphatically (Critica Botanica, Hort's translation, Aphorism 257, for example) that the Genus must be established before [specific] name is settled, so that in each genus we may recognise species which we are supposed to be distinguishing. For specific name is not given us alive, unless it has a head: head is generic name. It is not merely fanciful, surely, to believe that such an attitude was necessary in days when production of keys, and sound rules for nameformation, operation of which would produce agreed synonymies, was of first importance. But on other hand, his attitude to species is much more modern. Ramsbottom (1938) has given an excellent survey of Linnaeus's opinions and Svenson (1945) has discussed much of their historical background. Svenson points out that, as soon as (and not until) doctrine of a general and frequent transmutation of species had been brought into disrepute, species could be regarded with confidence as a morphologically stable group of individuals, breeding true. It then became a unit within genus, equally susceptible of definition. The idea of its constancy, doctrine of immutability of species, has been of great use in development of modern taxonomy. That Linnaeus in later years came to consider that species were not wholly immutable, as Ramsbottom has pointed out, does not mean that he returned to a chaos, comparatively speaking, of fluctuating forms within each genus. He, like his predecessors, knew far too many distinct species, apparently immutable apart phenotypical variation. Hybrids were to be recognised as such, but if they achieved relative constancy, then they merited status of species. These views are well expressed in his method of nomenclature. The generic name was a single word, denoting a general kind of plant or animal. His name for a species was a phrase, not exceeding twelve words and preferably as short as possible, which was descriptive. It either referred to some striking character by which species could be distinguished