七筋姑的细胞地理学研究

A CYTOGEOGRAPHICAL STUDY ON CLINTONIAUDENSIS (LILIACEAE)

根据本文对中国境内(从西藏聂拉木-吉林长白山)七筋姑10个居群的核型及细胞地理学和形态学分化的研究结果及前人的资料指出,东亚的七筋姑具有两种倍性,2n=14的二倍体和2n=28的四倍体。二倍体分布于云南～俄罗斯远东滨海边区,核型相当一致:K(2n)=2V+6J+2V+4j(2NOR+2j),2A(→2B)。四倍体除出现在东亚(或二倍体分布区)的两端——云南及其以西的喜马拉雅地区和日本外,目前仅在陕西南部化龙山北坡中山一带较狭的范围内发现。在东亚两端四倍体的核型为K(2n)=4V+12J+4v+8j(2NOR+6j),2A(→2B),且相当一致;在中部为K(2n)=4V+12J(2NOR+10J)+4v+8j[K(2n)=10m+16sm(2SAT)+2st],2A,二者核型具有相似性但有一定的差异。北美4种全部为2n=28,且核型一致。因此,七筋姑属的染色体基数x=7而非14。该属核型的原始类型在东亚,北美是该属的次生分化中心和现代分布中心。在东亚类群中,除种子随多倍化而增大,种子的颜色与地理分布有关外,很难从其它形态特征上作进一步区分。因此,主要以叶子大小、花序类型和花的数目,果实、种子的大小和颜色等特征作为Clintonia alpina或C.udensis var.alpina的分类依据是不充分的。

The genus Clintonia has four species in North America and one in eastern Asia ( Fig. 1). In this paper, the karyotypes and the intraspecific morphological and cytogeo-graphic differentiations of ten populations of C. udensis from China are analysed, and the probable origin area of the genus is also discussed. The conclusions are as follows: (l)Based on the chromosome numbers 2n = 28 from the North American species, the Japanese and Himalayan groups, the earlier investigators established x = 14 as the basic chromosome number of Clintonia, and they thought that there was no polyploid in this genus except for aneuploid only in C. borealis (Utech, 1975; Utech and Suda, 1975), but a few authors (Sen, 1975; Wang et al, 1993) pointed out the x = 7 basic number of this genus based on 2n=14 in C. udensis from Primorskiy Kray of Russia (Skolovskaya, 1966) and Yunlong, Yunnan Province of China (Wang et al, 1993) respectively. Our result along with the reports by previous authors (see table 1 )shows that at least two ploid levels exist in C. udensis, i. e. 2n = 14 and 2n = 28. The diploids are widely distributed from northwest Yunnan of China to Primorskiy Kray of Russia, while the tetraploids are located in northwest Yunnan, Himalayas, Japan, and a narrow area in Mt. Hualongshan of southern Shaanxi(07 population) (Fig. 2). Therefore, the basic chromosome number of Clintonia certainly is x = 7 rather than x=14, while 2n=28 in North America, Japan and Himalayan area are tetraploid, not diploid, According to the previous data, so far no diploid taxa of Clintonia has been found in North America and Himalayas. So we consider that the primitive type of Clintonia is in eastern Asia, and the secondary diversity center and the present distribution center of this genus are in North America. (2) C. udensis is widely distributed in eastern Asia (Fig. 2) ; it has two cytotypes. The karyotypes for all the diploid populations are remarkablely similar. Taken together, they can be roughly repersented by the formula: K (2n ) = 14 = 2V + 6J + 2v + 4j (2NOR + 2j). The chromosomes range in length 25. 55~12. 78 /urn, with the ratio of the longest to the shortest 2. 0. The karyotype belongs to Stebbins (1971)2A(2B). For the tetraploid taxa, except for 07 population, karyotypes are also identical and may be roughly symbolized as;K (2n) = 28 = 4V + 12J + 4v + 8j(2NOR + 6j). The length of chomosomes is from 27. 87 to 13. 93 fim, with the ratio of the longest to the shortest 2. 0, and thus the karyotype belongs to 2A(-,2B). The karyotype of 07 population is similar to those of above tetraploid taxa but also has some differences, especially in the position of satellites and the morphology of 10th and 14th pairs of chromosomes. Its formula is K(2n) = 28 = 4V+12J(2NOR + 10J) + 4v+ 8j(2n = 28=10m+16sm(2SAT) + 2st). The ratio of the longest (23. 72 fim)to the short-est(12. 97m) chromosomes is 1. 83. The Karyotype belongs to 2A. And the distribution range of this population is very narrow. We think that it is probably a recent evolutionary event in C. udemis. (3)Wether Clintonia in eastern Asia has 1 sp. or 2 spp. or 1 spp. and 1 var. has been debated for a long period. According to our observation, within C. udensis, only the size of seeds is related to its ploidy level, i. e. diploid individuals have smaller seeds and tetraploid ones have larger ones; the colour of seeds is related to its geographic distribution, i. e. the materials from the Himalayas through Yunnan, Sichuan to eastern Qinling Range have pale brown seeds, while those from Mt. Liiliang, Shanxi Province via Hebei, Liaoning, Jilin to Siberia and Japan have dark brown seeds. Some other morphological characters, such as the size of leaves and fruits, inflorescence type and flower numbers between individuals in one locality, even within one populaion have evident variation. Therefore, we consider that evidence (see Table 4 )for separating C. alpina or C. udensis var. alpina from C. udensis is not sufficient.