中国木兰科11属40种植物的核形态研究

A karyomorphological study of 40 species in 11 genera of the Magnoliaceae from China

为了探讨木兰科属间系统学关系和一些种的分类学地位,对中国木兰科11属40种进行了核形态研究。所研究的20种木莲属植物都为二倍体,表明木莲属植物主要是在二倍体水平上进化的,不同的种类具有各自的遗传组成,细微的染色体结构变异可能导致种间形态发生了明显的变化。木兰属的染色体数目具多样性,表明属内存在着不同倍性水平上的进化,说明木兰属分布广泛、形态复杂多样有其细胞学基础。细胞学证据支持木莲属应为独立的属,不宜于归并到木兰属。已观察的含笑属都为二倍体,而木兰属玉兰亚属的大多数种类为多倍体。我们认为维持现有的含笑属的分类地位和范围是恰当的,不支持将含笑属和玉兰亚属合并为一属。拟单性木兰属都是多倍体。木兰科植物形态特征重叠,性状呈网状进化,细胞学证据在探讨一些大属属下种的分类地位时具有一定价值,但论及整个科的分类系统和属间亲缘关系时,作用比较微弱。本文在细胞学基础上,结合形态和地理分布,重点对木莲属一些种类的分类地位进行了讨论。

In this paper, 40 species in 11 genera of the Magnoliaceae from China were karyomorphologically investigated for a better understanding of the intergeneric relationships in the family and the systematic positions of some species, particularly those in the genus Manglietia. The 20 Manglietia species studied are all diploid with 2n=38, indicating that in this genus the speciation may have taken place predominantly at the diploid level and that minor structural changes of chromosomes may have resulted in distinct morphological divergence. In the genus Magnolia, cytotypes with various ploidy levels from 2x to 6x have been found, which may be, at least to some degree, associated with the wide distributional range and complex gross-morphological variation of the genus. Our results indicate that Manglietia should be an independent genus from Magnolia and do not support the treatment of merging them as a genus. All the Michelia species already with chromosome numbers are diploid with 2n=38, while most of the species in Magnolia subgen. Yulania are polyploid, suggesting that Michelia is not closely allied with Yulania and that the two groups should not be merged as a genus. All Parakmeria members are polyploid. It is noteworthy that cytological evidence is generally less informative in clarifying the intergeneric relationships of the Magnoliaceae than the interspecific relationships within a given genus of the family because reticulate evolution may have extensively occurred in this family. Systematic positions of some species in Manglietia are discussed based on evidence from cytology, morphology and geographical distribution.