Gene duplications in Eupatorium and their systematic implication

泽兰属（菊科）间断分布于北美洲和东亚。该属的二倍体物种具有10对形态分化的体细胞染色体，在细胞遗传学上处于二倍体或双二倍体状态。10号染色体是真芋族许多属中常见的染色体数目，一直被认为是该族的基本染色体数目。然而，这项研究发现，泽兰属的二倍体物种（包括亚洲和美洲）具有编码7种酶的基因的广泛重复，这些酶在酶电泳中被常规检测。这一结果表明，多倍体起源的属和族泽兰族。利用叶绿体NA的限制性片段长度多态性，证实了佩兰族起源于普遍存在单倍体染色体数目大于10的向日葵族。因此，在泽兰族中普遍存在的单倍体染色体数目10可能是从向日葵族中的较高数目减少的。目前正在进行进一步的研究来检验这一假设。

Eupatorium (Compositae) disjunctly occurs in North America and East Asia. Diploid species of the genus have ten pairs of morphologically differentiated somatic chromosomes and are cytogenotically in diploid or amphidiploid condition. The haploid number 10 is common among many genera in the tribe Eufatorieae and had been regarded as the basic chromosome number of the tribe. This study, however, uncovered that diploid species of Eupatorium (both Asian and American) have extensive duplications of genes encoding seven enzyme species which are routinely examined in enzyme electrophoresis. This result suggests polyploid origin of the genus and also of the tribe Eupatorieae. Using the restriction fragment length polymorphism of chloroplast NA, it is confirmed that the tribe Eupatorieae is derived from the tribe Heliantheae in which haploid chromosome numbers more that ten are prevalent. Thus haploid chromosome number ten prevailing in the tribe Eupatorieae is probably reduced from higher numbers in the tribe Heliantheae. Further study to test this hypothesis is now in progress.