Polyploidy in Angiosperms: Monocotyledons

Abstract

Several different estimates of polyploid frequency in angio-sperms have been made, including G.L. Stebbins’ (1,2) figure, first published in 1950, of 30–35%, and suggestions by M.J.D. White in 1942 (3) of at least 40%, and by Grant in 1963 (4) of 47%. These figures represent different ways of calculating Polyploidy and different interpretations of the meaning of the word in the context of plant systematics. Stebbins’ estimate includes as polyploid those species which have gametic chromosome numbers that are multiples of the basic diploid number found in their genus, in other words, intrageneric Polyploidy. White’s figure is based on the simple observation that even haploid numbers exceed odd by about 40% and he thus assumed this 40% to be largely attributable to a polyploid origin. Grant postulated that species with haploid numbers in excess of n=13 would mainly be polyploid and those with n=13 or less, predominantly diploid. Grant’s study also included the only estimate I have encountered of Polyploidy in each of the two subclasses of angiosperms. He calculated a frequency of 43% in Dicotyledonae and a much higher 58% in Monocotyledonae. These figures were based on chromosome data accumulated by 1955 for some 17,138 species.

This work was supported by grant DEB 78-10655 from N.S.F.

I thank G. Davidse, T. Croat, R.W. Faden, and H.E. Moore for their advice on particular groups.