Extensive chromosome number variation in Aster ageratoides var. pendulus (Asteraceae)

Abstract

Aster ageratoides var. pendulus, a recently described taxon, is endemic to Mt Hupingshan of north-western Hunan, China. Field observations and collections were made from the only known population. Root-tip squashes were used to determine the chromosome numbers of 96 plants and 61 seedlings from the achenes of eight sample plants. The results show that var. pedulus is a swarm of 30 cytotypes with nearly continuous chromosome numbers from 2n=60 to 2n=92. Chromosome numbers of 61 seedlings vary from 2n=61 to 2n=91, belonging to 18 cytotypes. The chromosome number variation of var. pendulus is highly unusual not only in the A. ageratoides polyploid complex but also in angiosperms. Such an enormous continuous variation of chromosome numbers could have arisen by the combined effect of hybridization, recent origin and high levels of polyploidy. © 2011 The Linnean Society of London.