Chromosome studies in the grass subfamily Chloridoideae. II. An analysis of polyploidy

Polyploidy is frequent among the grasses. This study indicates that it has a high frequency in the subfamily Chloridoideae, where more than 90% of the studied specimens are polyploids. These levels range from diploid (2n = 20 for x = 10 and 2n = 18 for x = 9) to 16-ploid (2n = 160) for x = 10 in Ctenium concinnum Nees and 20-ploid (2n = 180) for x = 9 in Hilaria mutica Benth. This polyploid trend is seen in southern Africa, as well as worldwide. Analysis indicates that many polyploids are alloploids, suggesting extensive hybridization within this group. This is supported by the presence of apomixis in many members of the subfamily. Both polyploidy and apomixis are thought to be important evolutionary mechanisms in Chloridoideae as well as closely related Panicoideae, and have a high frequency in southern Africa. Due to the stable ecological, geographical and climatological history of Africa, the continent is ideally suited for the stabilization of hybrid complexes by means of apomixis and polyploidization.