Molecular Systematics of Eupatorieae in New World

在真核生物中，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)根据在野马追中广泛复制基因的证据推测，该族是多倍体起源的，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学研究。为了获得用于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，并用生菜叶绿体DNA探针检测RFLP。以向日葵属和向日葵属为外类群构建了一个分支图，在RFLP数据集上的分支分析结果表明，菊科起源后出现了两个分支：一个包括Ageratina(n=17)和Neomirandia(n=17，25)，另一个包括Mikania(n=16-18)、Stevia(n=11)、8属(n=10)和Brickellia(n=9)。这一结果支持了n=10源于较大染色体数目的假设。CpDNA数据表明，真菊亚科植物来源于向日葵亚科。在向日葵亚科中，有研究表明，向日葵亚科中n=16的属是由其祖先属中的n=8种派生而来的。在Eupatorieae中，已知一些墨西哥属的n=16。最近获得了这些属之一Bartlettina的材料，该属的分子系统分析正在进行中。

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.