Poaceae

Abstract

Bothalia 32,1: 1 2 3 -1 2 6 (2 002) Miscellaneous notes POACEAE CHROMOSOME STUDIES ON AFRICAN PLANTS. 16. POLYPLOIDY IN THE GENUS EHRHARTAThe genus Ehrharta Thunb. comprises ± 36 species of which 20 are endemic to the winter rainfall area of South Africa (Verboom 2000). The genus belongs to the tribe Ehrharteae, which has been shuffled betw een the Phalarideae and the O ryzeae, the Ehrharteae and Arundineae of the Arundinoideae, the Ehrharteae of the Oryzoideae, and the Ehrharteae and the Oryzaneae of the Bambusoideae (Gibbs Russell & Ellis 1987). Recently the Ehrharteae was moved from the Arundinoideae (Renvoize 1981) to the Bambusoideae (Renvoize 1985; Watson et al. 1985). Linder & Ellis (1990) found no other representatives of the Bambusoideae present in the Fynbos Biome. Inclusion of the tribe Ehrharteae in the Bambusoideae rests on the presence of non-anatomical characters such as bambusoid embryos and lodicules (Renvoize 1985; Clayton & Renvoize 1986). Currently the E hrharteae form s part o f the 'B EP' clade (Bambusoideae, Ehrhartoideae and Pooideae) in grass phylogenetics (Clark et al. 1995).The presence of many endemic species and the absence of any close relatives to Ehrharta in South Africa, may present us with some answers to the forma tion of polyploidy in grasses. Polyploidy is a common phenomenon among the grasses and Stebbins (1985) sug gested that more than 80% of species in this family have undergone some form of polyploidy somewhere in their evolutionary history. In an attempt to determine the degree of polyploidy in South African grasses, our labora tory has studied chromosome numbers of various grasses and the results were mostly published in this series.One of the genera that has been extensively studied, is the genus Ehrharta. Various chromosome number reports for the genus Ehrharta have been published (Avdulov 1931;Nakamori 1933: Parthasarathy 1939Love 1948;Stebbins 1949: Raven et al. 1965Tateoka 1965: Fernandes & Queiros 1969: Stebbins 1985Spies & Du Plessis 1986: Hoshino & Davidse 1988 Spies & Voges 1988; Spies et al. 1989). This report includes additional results from collections from 37 populations, representing nine different species or subspecies and includes first counts for three species and one subspecies. These new counts are combined with the published results (in total more than 100 specimens have been studied) in an attempt to determine the degree of polyploidy within this genus.