Molecular Systematics of Eupatorieae in New World

在拟鸟中，n=10是普遍存在的，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。Yahara等人（1991）基于在n=10的紫茎泽兰中广泛存在基因重复的证据，假设该部落是多倍体起源，n=10来自较大的染色体数目。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研究。为了获得分子系统研究所需的植物材料，我们在德克萨斯州和哥斯达黎加进行了野外工作。从这些材料中分离总DNA，并利用生菜叶绿体DNA探针检测RFLPs。以向日葵科的Clibadium和Coreopsis为外类群，构建了一个枝状图。通过对RFLP数据集的演化分析，发现在长喙亚科起源之后，出现了两个分支；一个属包括Ageratina （n=17）和Neomirandia (n=17、25)，另一个属包括Mikania （n=16 ~ 18）、Stevia （n=11）、8个属（n= 10）和Brickellia （n=9）。这一结果支持了n=10来自较大染色体数目的假设。cpDNA数据已经表明，Eupatorieae是由Heliantheae衍生而来。在Heliantheae中，有人认为Heliantheae中n=16的属来源于n=8的祖先属。本研究结果表明，Eupatorieae来源于Heliantheae中n=16的种。在Eupatorieae中，一些墨西哥属已知有n=16。最近获得了其中一个属Bartlettina的材料，目前正在进行该属的分子系统分析。

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.