J Syst Evol ›› 2005, Vol. 43 ›› Issue (6): 533-538.DOI: 10.1360/aps040037

• Research Articles • Previous Articles     Next Articles

A new basic chromosome number of x=7 for the genus Streptopus (Liliaceae)

ZHANG Ting, GU Zhi-Jian*   

  1. (Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650204, China)guzhijian@mail.kib.ac.cn
  • Received:2004-04-06 Published:2005-11-18

Abstract: Four populations of Streptopus simplex (Liliaceae) from western and northwestern Yunnan Province, China, were investigated cytologically. The chromosome count of the two populations growing in spruce forests from Bitahai and Xiaozhongdian, Shangri-La County (formerly Zhongdian County), northwestern Yunnan, was 2n=16 with x=8, confirming the previous counts for this species, but the count of the two populations growing in alpine scrubs, one from Pianma, Fugong County, and the other from Gongshan County, both of western Yunnan, was 2n=14 with x=7, which represents a new count for the species and a new basic number for the genus. The karyotypes of the two populations from Shangri-La were formulated as 2n=4m+8sm+4st and 2n=8m+2sm+6st, respectively, with the chromosomes changing in size gradually from the largest to the smallest one, and those of the other two populations were formulated as 2n=14=4m+10sm, and 2n=14=7m+7sm, respectively, with the first pair of chromosomes being median-centromeric (m) and markedly larger than the remaining ones. As the basic chromosome number of x=8 is the commonest one in the genus Streptopus, this might be considered as the original number whereas the number of x=7 the advanced one. The presence of one pair of much larger chromosomes yet one less pair of smaller subterminal-centromeric (st) ones in the chromosome complement of the x=7 populations suggest that this number may have been derived from x=8 through the Robertsonian fusion of centromeres.

Key words: Streptopus simplex, chromosome number variation, Roberstonian fusion.