Molecular Systematics of Eupatorieae in New World

在泽兰族中，n=10是普遍存在的，并被认为是一个基本的染色体数目。然而，有些属的n= 15，16，17和25。基于n=10的泽兰属中广泛的基因重复的证据，Yahara等人（1991）假设该族是多倍体起源，n=10是由较大的染色体数目衍生的。为了验证这一假设，我们对n= 9，10，11，17和25的属进行了分子系统学研究。为了获得分子系统学研究的植物材料，我们在德克萨斯州和哥斯达黎加进行了野外工作。从这些材料中提取总DNA，并使用莴苣叶绿体DNA探针检测RFLP。以向日葵亚科的Clibadium和Coreopsis为外类群构建了一个分支图，通过对RFLP数据集的分支分析表明，在泽兰族起源后，这两个分支发生了分化;另一种包括薇甘菊属（16-18）、甜叶菊属（11）、八属（10）和Brickellia属（9）。这一结果支持了n=10来自较大染色体数目的假设。cpDNA数据表明泽兰族起源于向日葵族。在向日葵亚科中，有人认为向日葵亚科中n=16的属是由n=8的祖先属衍生而来的。本研究结果表明，泽兰族起源于向日葵族的n=16种。在泽兰族中，一些墨西哥属已知有n=16。其中一个属的材料，巴氏藻属，最近已经获得，该属的分子系统学分析正在进行中。

In Eupatorieae, n=10 is prevailing and has been considered to be a basic chromosome number. However, some genera have n=15,16,17 and 25. Based on evidence of extensive gene duplications in Eupatorium with n=10,Yahara et al (1991) postulated that the tribe is of polyploid origin and n=10 is derived from larger chromosome numbers. To test this hypothesis, We carried out molecular systematic study on genera with n=9,10,11,17, and 25.To obtain plant materials for molecular systematic studies, we carried out field works in Texas and Costa Rica. Total DNAs were isolated from these materials and RFLPs were detected using probes of lettuce chloroplast DNA. Clibadium and Coreopsis of Heliantheae were used as outgroups to construct a cladogram.As a result of cladistic on RFLP data sets, it is shown that two clades were diverged after the origin of the Eupatorieae ; one including Ageratina (n=17) and Neomirandia (n=17,25), and the other including Mikania (n=16-18),Stevia (n=11), eight genera with n=10, and Brickellia (n=9). This result supports the hypothesis that n=10 is derived from larger chromosome numbers. It is already shown from cpDNA data that Eupatorieae is derived from Heliantheae. In Heliantheae, it has been suggested that genera with n=16 in Heliantheae are derived from ancestral genera with n=8. The result of this study suggests that Eupatorieae isderived from species with n=16 in Heliantheae. In Eupatorieae, some Mexican genera have been known to have n=16. Materials of one of those genera, Bartlettina, have been recently obtained and molecular systematic analysis of this genus is now ongoing.