Molecular Systematics of the Asteridae

密歇根大学（University of Michigan）的杰弗里·帕尔默（Jeffrey Palmer）博士及其同事正在两个不同的分类水平上研究开花植物之间的进化关系。在一个层面上，他们计划调查构成菊科亚纲的50多个科之间的关系，菊科是菊科的第二大亚纲。尽管Asteridae通常被认为是dicots亚纲中最先进和最近进化的，但关于这一类群中大多数科的相对位置和关系仍然存在悬而未决的问题和争议。此外，对于这个群体作为一个整体是自然的、单系的还是平行衍生物的组合，存在根本性的怀疑。帕尔默将利用最近发展的分子系统分析技术，为这个亚纲构建一个详细的系统发育，以此来解决这一争议。他将研究这一群体的分布，并确定一些确定的叶绿体DNA重排的系统发育意义。他还将研究编码关键光合酶二磷酸核酮糖羧化酶大蛋白亚基的叶绿体基因的序列变异。第二组研究涉及对菊科茄科亚纲茄科属和部落的详细分子系统发育的构建。这将极大地帮助我们理解这个亚纲中经济上最重要的科，也是最大的科之一的进化趋势和关系。尽管对这一重要植物群（包括马铃薯、西红柿和辣椒等重要作物）的生物学和系统学进行了广泛的研究，但关于这一科的分类关系仍然存在根本性的分歧。Palmer的方法将包括叶绿体DNA限制性内切位点突变的比较图谱和基于这些叶绿体DNA突变的计算机辅助系统发育树的构建。

Dr. Jeffrey Palmer and colleagues at the University of Michigan are studying evolutionary relationships among flowering plants at two distinct taxonomic levels. At one level, they plan to investigate relationships among the 50 or so families that comprise the subclass Asteridae, the second largest subclass of dicots. Although Asteridae are generally considered to be the most highly advanced and recently evolved of dicots subclasses, outstanding questions and controversies remain concerning the relative placement and relationships of most of the families in this group. In addition, there are fundamental doubts about whether the group as a whole is a natural, monophyletic one or an assemblage of parallel derivatives. Palmer will address this controversy by constructing a detailed phylogeny for the subclass using recently developed techniques of molecular systematic analysis. He will examine the distribution within this group and determine the phylogenetic significance of a number of defined chloroplast DNA rearrangements. He will also examine sequence variation in the chloroplast gene encoding the large protein subunit of the key photosynthetic enzyme, ribulose bisphosphate carboxylase. The second set of studies involves construction of a detailed molecular phylogeny for genera and tribes of the family Solanaceae of subclass Asteridae. This will greatly aid our understanding of evolutionary trends and relationships in this, the economically most important family in the subclass and also one of its largest. Despite the wide range of studies conducted on the biology and systematics of this important group of plants, which includes such vital crops as potatoes, tomatoes, and chili peppers, fundamental disagreements still exist regarding taxonomic relationships in the family. Palmer's approach here will involve comparative mapping of chloroplast DNA restriction site mutations and computer-assisted construction of phylogenetic trees based on these chloroplast DNA mutations.