Dissertation Research: Molecular Phylogenetics and Interfamilial Relationships in the Portulacaceous Alliance of the Order Caryophyllales

小行星9701125 在爱荷华州州立大学的罗伯特·华莱士博士的指导下，研究生温迪·阿普尔奎斯特正在利用爱荷华州州立大学多年来积累的植物园材料和野外收集资料，研究Basellaceae、Cactaceae、Didieaceae和Portulacaceae这四个cartilallalean家族中植物的系统发育或谱系关系。传统上用于植物分类的花和果实的形态特征，特别是C。500种马齿苋（马齿苋科），被怀疑是不可靠的标记进化组，也许是由于重复，收敛适应干旱或沙漠栖息地。叶绿体基因组DNA序列的新证据正在寻求提供大量的变量，但提供信息的字符（突变或核苷酸取代），可用于测量这些植物之间的遗传分化。反过来，一个可靠的系统发育框架，这些植物将使他们的历史地理和适应世界各地的沙漠地区的模式的研究。 传统上被认为是上述四个卡氏藻科的植物，在进化、地理学和适应方面存在着有趣的问题，这些植物大多生长在世界上干旱或沙漠的栖息地，主要分布在南美洲、非洲和澳大利亚的南部大陆。如果没有一个可靠的种群发生学，根据不直接受栖息地条件影响的遗传特征，就不可能将古代大陆漂移造成的模式与最近的扩散和迁移分开。这个项目是一个集中的努力，构建一个系统发育框架，这些植物的DNA序列信息，增强了形态，染色体和解剖数据在手。

9701125 Wallace Graduate student Wendy Applequist, under the guidance of Dr. Robert Wallace at Iowa State University, is studying the phylogenetic or genealogical relationships of plants in the four caryophyllalean families of Basellaceae, Cactaceae, Didiereaceae, and Portulacaceae, making use of botanical garden materials and field collections amassed over the years at Iowa State. The morphological features of flowers and fruits used traditionally in the classification of these plants, especially the c. 500 species of purslanes (Portulacaceae), are suspected to be unreliable in marking evolutionary groups, perhaps due to repeated, convergent adaptations in arid or desert habitats. New evidence from DNA sequences of the chloroplast genome is being sought to provide a large number of variable yet informative characters (mutations or nucleotide substitutions) that can be used to measure genetic divergences among these plants. In turn, a reliable phylogenetic framework for these plants will enable the study of their historical biogeography and patterns of adaptation to various desert regions of the world. The plants traditionally treated in the four caryophyllalean families listed above present interesting problems of evolution, biogeography, and adaptation, mostly in arid or desert habitats of the world, and primarily on the southern continents of South America, Africa, and Australia. Disentangling patterns caused by ancient continental drift from more recent dispersals and migrations has been impossible without a reliable phylogeny for the group, based on genetic features not directly affected by habitat conditions. This project is a focused effort to construct a phylogenetic framework for these plants from DNA sequence information, augmented by the morphological, chromosomal, and anatomical data in hand.