我国入侵植物薇甘菊(菊科)的细胞学研究

为了解入侵植物薇甘菊(Mikania micrantha)的细胞学特性,研究了薇甘菊在我国广东东南部4居群和台湾2居群的染色体数目和染色体形态。结果表明,所有居群的薇甘菊染色体数目均为2n=36,第一对染色体为近中部着丝粒染色体,其长臂中部具有次缢痕,显著大于其余染色体。广东深圳大学和深圳水库居群的核型公式为2n=20m+14sm+2st;广东汕头、阳江和台湾屏东居群为2n=22m+12sm+2st;台湾宜兰居群为2n=18m+16sm+2st。此前有报道薇甘菊深圳大学居群的染色体数目为2n=38,推断为制片过程中第一对染色体从次缢痕处断裂而导致的计数错误。因此,薇甘菊虽存在非整倍性和多倍性变化,但在广东东南部和台湾的入侵居群中目前仅发现基于x=18的二倍体(2n=36),该种在这些地区的成功入侵与多倍性无关。

Cytology of Mikania micrantha (Asteraceae), An Invasive Plant in China

In order to reveal the cytology characters of Mikania micrantha (Asteraceae), the chromosome number and morphology of Mikania micrantha (Asteraceae), an invasive plant in China, were studied, including Shenzhen University, Shenzhen Reservoir, Shantou and Yangjiang populations from south-east Guangdong, and Pingdong and Yilan populations from Taiwan. The chromosome number 2n=36 was determined for all six populations. Their karyotypes were all characterized by having a remarkably larger, submedian centromeric chromosome pair with a secondary constriction in the middle of the long arms. The karyotype formulas were as follows: 2n= 20m+14sm+2st for both Shenzhen University and Shenzhen Reservoir populations, 2n=22m+12sm+2st for Shantou, Yangjiang and Pingdong populations, and 2n=18m+16sm+2st for Yilan population. The only previous report of chromosome number for M. micrantha from its invasive range in China, i.e. 2n=38 of Shenzhen University population, is most likely a miscount, which may have been caused by mistaking the two chromosomal fragments formed through breakage of the largest chromosome pair at secondary constrictions as two whole chromosomes. Results of our study and those previously reported from the native range of M. micrantha indicate that there indeed exists aneuploid and polyploid variation within this species, but 2n=36 (diploid based on x=18) is the only number currently known from the invading populations in China. It seems that at least in south-east Guangdong and Taiwan, China, the successful invasion of M. micrantha is not associated with polyploidy.