中国西南六种广义拂子茅属( 禾本科) 植物的染色体数目

广义拂子茅属( Calamagrostis) 是一个世界温带广布的大属, 有些作者又分为拂子茅属和野青茅属, 但近期的研究表明处理为一个属较为合适。中国共有37 种广义拂子茅属植物, 但至今没有任何染色体的研究。本文报道了其中产于中国西南6 种野青茅的染色体数目, 其中Deyeuxia petelotii 4 个居群, D1 diffusa, D1 moupinensis, D1 nivicola 和D1f lavens 各一个居群都是四倍体( 2n= 4x= 28) , D1 neglecta 为六倍体( 2n= 6x= 42) 。根据广义拂子茅属植物染色体倍性特征, 该属植物中至今未发现二倍体, 四倍体是该属中倍性最低和最普遍的, 广义拂子茅属的演化很可能是在四倍体的水平上进行的。由于以上几个四倍体种均是狭域分布的类群, 所以可能是由四倍体的祖先隔离分化形成的。

Chromosome counts in the Genus Calamagrostis s1l ( Poaceae) from Southwestern China*

Calamagr ostis s1l. is a large genus widespread throughout the world in temperate and cold regions. It is sometimes divided into two genera: Calamagr ostis s. str . and Deyeuxia, and both have been accepted in China, while recent studies
show it should be treated as one genus. There are 37 species of Calamagrostis s1 l. occuring in China, but no cytological study was conducted before. In this paper the chromosome numbers of 9 populations representing 6 species of Deyeuxia ( recognized as a part of Calamagrostis s1l. ) from southwestern China are reported for the first time. Most of them are tetraploids and no diploid species is found. All 4 populations of D1 petelotii and each population of D1 diff usa, D1 moupinensis , D1 nivicola, and D1flaven are tetraploids ( 2n= 4x= 28) , and the only population of D1 neglecta is hexaploid ( 2n= 6x= 42) . On the basis of these counts and previous reports, tetraploid is again confirmed primitive in Calamagrostis s1l. and the speciation of the genus is principally occurred at tetraploid level in this region. As these five tetraploid species are restricted to Himalayan-Hengduan Mountains, they probably have been formed by isolation from tetraploid ancestors.