NOTES ON THE CLASSIFICATION AND DISTRIBUTION OF GENERA RELATED TO GOSSYPIUM

Abstract

HUTCHINSON united by clines maintained by gene exchange over a continuous distribution, these ecotypes are genetically unstable and depend for their continued existence on the continuance of the selective forces that brought them into being. If the continuity of the distribution is broken, divergence both under different selective forces and at random (the Sewall Wright (1940) effect) will take place and will be irreversible, and a real discontinuity will arise which will justify recognition as of specific rank. Such a new species may remain small and uniform, adapted to its particular ecological niche, but not spreading. Alternatively, by the development of a new character or by some accident of tbe environment that opens up a considerable area which it is well fitted to colonize, it may multiply and spread. The genetic consequences of evolutionary success have been discussed by Hutchinson & Stephens (1947Z)), who have concluded that once the process of multiplication and variation has begun, it will tend to be cumulative, so that a successful species will become variable and, having become variable, it will have the capacity to respond to selection that is the condition of further success. Naturally, it will be in the areas of the initial success that the greatest variability will be built up, and the distribution of variability which Vavilov (1935) found in successful crop plants may therefore be regarded as a genetic consequence of evolutionary success that is valid for any species, and is not confined to cultivated organisms. If this view of the process of species development is accepted, related forms that are wholly 'sympatric', to use Mayr's term, can only be regarded as specifically distinct if the existence of some other isolating mechanism (e.g. polyploidy) is demonstrated. Moreover, where distinct, but related, species are partially sympatric, it should generally be possible to sbow that their distributions were originally distinct, and only overlapped after successful spread from their original centres. The wild species of Gossypium meet these requirements, since they are in general well isolated. In Cienfugosia and Thespesia, however, many of the forms that have been given specific rank are sympatric. Examination of herbarium material and of published descriptions showed that sympatric species were often difficult to separate, or were regarded by some authors as synonymous. A wider interpretation of the species has been adopted here and it will be shown that the genera can be divided into natural species which now occupy, or give evidence of having originated in, geographically distinct areas. Moreover, the distribution of the variability within these species is as would be expected if Vavilov's principle applies. THE RELATIONSHIPS OF THE GENERA Edlin (193s) has proposed that the Malvaceae should be confined to genera with septicidally dehiscent schizocarpic fruits, genera with loculicidally dehiscent capsular, or baccate, fruits, being included in the Bombacaceae. The whole of the Hibisceae, in whi...

A Revision of Gossypium Sect. Grandicalyx (Malvaceae), Including the Description of Six New Species

“…More recent interpretations (Fryxell 1969b(Fryxell , 1979Mauer 1954;Prokhanov 1947;Valicek 1979Valicek , 1981 have included these Kimberley species in Gossypium, except for Hutchinson (1947aHutchinson ( , 1947b, who accepted Lewton's genus Notoxylinon. Saunders (1961) omitted the Kimberley cottons from his treatment for lack of material for study.…”

“…The next species to become known (G. pulchellum (C. A. Gardner) Fryxell) Alef., Thespesia Sol. ex Correa, and Gossypium; none of the seven is included in a contemporary circumscription of Cienfuegosia (Hutchinson 1947a;Fryxell 1969aFryxell , 1979, which has no Australian representatives.…”

Las especies austroamericanas del género <i>Cienfuegosia</i> Cav. (Malvaceae-Gossypieae)

“…J.B. Hutchinson (1947a) en su estudio sobre los géneros relacionados con Gossypium, acepta la idea de Lewton (1915) y reconoce 11 especies pertenecientes a Cienfuegosia.…”

Molecular systematics in Gossypium and its relatives

“…(Hutchinson 1947). The Hawaiian endemic Kokia Lewton includes four species, of which one is extinct (Lewton 1912;Degener 1934;Hutchinson 1947). In addition to these four small genera, the tribe includes four moderate sized genera with broader geographic ranges.…”

“…B. Hutch. (Hutchinson 1947). The Hawaiian endemic Kokia Lewton includes four species, of which one is extinct (Lewton 1912;Degener 1934;Hutchinson 1947).…”