Molecular Systematics of the Malpighiaceae

木兰科是热带和亚热带的一个中等大小的开花植物科，约有65属1200种，其中85%的物种原产于新大陆，其余的物种分布在古热带。这个家庭内部是同质的，外部是孤立的，也就是说，所有的成员看起来都很相似，有明显的血缘关系，但与其他任何家庭都不太相似。由于上述相似性，主要依靠大体形态的传统系统方法无法解决该科内部的许多关系问题，也无法揭示该科属于较大的非专门化开花植物(与玫瑰族相关)的位置，这些植物的花在五个轮生的花序中具有离生部分。北卡罗来纳大学的马克·蔡斯博士和密歇根大学的威廉·安德森博士提出的这项研究旨在将新的分子技术应用于这些古老而棘手的问题。绿色植物的叶绿体包含大量的环形染色体，这些染色体相对容易确定，因为它们含有的DNA比巨大的核基因组少得多。近年来，一些研究人员在利用叶绿体DNA(CpDNA)的比较研究来解决植物系统学问题方面取得了巨大的成功。蔡斯博士和安德森博士计划用两种截然不同的方式研究木犀科和几个可能有亲缘关系的科的代表的cpDNA，试图回答有关科内和科间关系的问题。对选定的cpDNA基因进行核苷酸测序将允许构建一个关于马兜铃科及其近缘家族的信息性系统发育假说。然后，他们计划使用限制酶切点图谱技术，比较60种木兰科植物的cpDNA，这些物种代表了该科中最具多样性的物种。科内的系统发育将解决这样的问题：功能相似甚至形态相似的水果是一次还是几次平行进化；属之间是如何相互联系的；关于科的起源和最早成员的性质的两个截然相反的假说中，哪一个是正确的。这两个工作者之间的合作结合了传统形态系统学和现代分子方法的优点，应该成为其他传统和分子系统学家未来合作的典范。

The Malpighiaceae are a medium-sized family of tropical and subtropical flowering plants, comprising about 65 genera and 1200 species, with 85% of the species native to the New World, the rest found in the Paleotropics. The family is internally homogeneous and externally isolated, that is, the members all look a great deal alike and are clearly related, but do not closely resemble any other family. Traditional systematic methods, relying principally on gross morphology, have failed to resolve many questions of relationships within the family, because of the aforementioned similarity, and also to reveal where this family fits into the larger group of relatively unspecialized flowering plants (related to the rose group) whose flowers have free parts in whorls of five. The research proposed by Dr. Mark Chase at University of North Carolina and Dr. William Anderson at University of Michigan is designed to apply new, molecular techniques to these old, intractable problems. The chloroplasts of green plants contain numerous circular chromosomes, which are relatively easy to characterize because they hold so much less DNA than the huge nuclear genome. Several researchers have had great success in recent years at using comparative studies of chloroplast DNA (cpDNA) to resolve problems in plant systematics. Drs. Chase and Anderson plan to study the cpDNA of the Malpighiaceae and representatives of several putatively related families in two quite different ways, attempting to answer questions about relationships within the family and between families. Nucleotide sequencing of selected cpDNA genes will allow construction of an informative phylogenetic hypothesis for Malpighiaceae and related families. Then, using the technique of restriction site mapping, they plan to compare the cpDNA of 60 species of Malpighiaceae that represent most of the diversity within the family. The within- family phylogeny will resolve questions about whether functionally analogous and even morphologically similar fruits have evolved once or several times in parallel; how the genera are related to one another; and which of two diametrically opposed hypotheses about the place of origin of the family and the nature of the earliest members is correct. Collaboration between the two workers, which combines the strengths of traditional morphological systematics with a modern molecular approach, should serve as a model for future collaboration between other traditional and molecular systematists.