The Cytogeography of Aster ageratoides var. laticorymbus (Asteraceae), a Polyploid Complex Endemic to China

中國特有植物寬傘三脈紫菀的細胞地理學

黎維平(Wei-Ping Li)

《Botanical Bulletin of Academia Sinica》 46卷4期 (2005/10) Pp. 355-361

https://doi.org/10.7016/BBAS.200510.0355

摘要

寬傘三脈紫菀分佈於華西南至華東地區。在其整個分佈範圍內，對26個野生居群進行取樣和染色體計數。本文還首次對分別代表3種細胞型的6個居群進行了核型分析。結果顯示，該變種是一個具有3種細胞型（2x，4x和6x）的多倍體複合體，其中以六倍體(2n=6x=54)為主。六倍體廣布於華西南至華東地區，而二倍體(2n=2x=18)和四倍體(2n=4x=36)較為少見，分佈限於雲貴高原的局部地區及其臨近地區。基於該複合體的細胞地理分佈、核型分析、與地理分佈有關的形態變異以及先前的一則報導，作者提出以下建議：(1)該複合體的多倍體可能是同源多倍體，並且四倍體兩次獨立起源；(2)從某些核型參數來看，不同倍性的細胞型進化速度有差異；(3)雲貴高原是該複合體的多樣性中心和起源中心。該複合體的擴散路線是從雲貴高原擴散到華東地區；(4)以六倍體為主的分佈模式的形成可能歸因於競爭排斥和六倍體高度的擴散能力及佔領新生境的能力；(5)該變種是一較為年輕的複合體。

關鍵字

寬傘三脈紫菀 ； 擴散路線 ； 分佈模式 ； 核型 ； 多倍體複合體 ； 雲貴高原

並列摘要

Aster ageratoides var. laticorymbus is distrubuted from southwestern China to eastern China. Population sampling across its whole distribution area was made in its twenty-six populations. Chromosome numbers of all the populations were investigated, and six populations, representative of various ploidy levels, were analyzed karyotypically for the first time. The results show that this variety is a polyploid complex comprised of 2x, 4x and 6x. The populations are mostly hexaploid (2n=6x=54) and occupy an extensive area from southwestern China to eastern China while the diploid (2n=2x=18) and the tetraploid (2n=4x=36) are less frequent and limited to narrower regions of the Yunnan-Guizhou Plateau and the transitional belts from the plateau to adjacent areas. Based on the cytogeographical distribution of the complex, the analysis of its karyotypes, its morphological variations related to geography and a previous report, some hypothesis are made: (1) the polyploids of the complex might be autopolyploids, and the tetraploid might have originated independently twice; (2) in terms of some karyotypical parameters, different ploidy levels of the complex evolved at different speeds; (3) the Yunnan-Guizhou Plateau is the diversity center and the origin center of the complex, and the place from which the hexaploid dispersed eastwards to eastern China; (4) the distribution pattern that the hexaploid is dominating might have been formed by the competitive exclusion and its high capability to disperse and occupy new habits; and (5) the variety is a relative young complex.

並列關鍵字

Aster ageratoides var. laticorymbus ； Dispersal route ； Distribution pattern ； Karyotype ； Polyploid complex ； Yunnan-Guizhou Plateau