微糙三脉紫菀的细胞地理学研究

Cytogeography of Aster ageratoides var.scabulus

三脉紫菀多倍体复合体一直被认为是一个困难的类群.但是,作为该复合体主产地的中国,其分类学研究和细胞学资料十分缺乏.因此,对微糙三脉紫菀9个居群进行了细胞学研究.结果显示,微糙三脉紫菀为四倍体(2n=4x=36),关于微糙三脉紫菀有六倍体的报道应属鉴定错误.微糙三脉紫菀6个居群的核型资料表明,其核型的不对称性具有经度地带性变异的趋势.据此认为,微糙三脉紫菀起源于浙皖山丘西部,然后向西扩散,抵达云贵高原和四川.这一假设得到横走地下茎演化证据的支持.

Aster ageratoides polyploid complex has been reputed t o be a difficult taxonomical subject.However,taxonomical study and cytological data on the complex from China,its main distribution region,are extremely scanty.Therefore,9populations of Aster ageratoides var.scaberulus Ling were investigated cytologically.The result shows that A.ageratoides var.scaberulus is a tetraploid with 2n=4x=36,and the reports that it pos-sesses a hexaploid likely came from m isidentification.Based on the fact that the karyotype variation of 6pop-ulations of A.ageratoides var.scaberulus is correlated with longitude,it cou ld be suggested that A.ageratoides var.scaberulus might be originated in western Zhejiang-Anhui Massif,and then disperse westwards,arriving at Yunnan-Guizhou Plateau and Sichuan.This hypothesis is supported by the evolutionary evidence of horizonta l rhizome of A.ageratoides var.scaberulus.