Dissertation Research: Systematics of Stylocline (Asteraceae)

在Rancho Santa Ana植物园的Loren Rieseberg博士的指导下，研究生Morefield正在研究美国西南部向日葵的亲戚Stylocline及其亲戚的几个物种，以评估这些一年生和高度近亲繁殖的植物种群内部和种群之间的遗传和基因组变异水平。主要的分析方法包括从植物中提取的可溶性酶的蛋白质电泳样品差异，以及DNA分析方法来测量核糖体基因和叶绿体基因的突变差异。几个相关的植物类群也将被研究，以建立一个系统发育框架，表明物种之间的进化关系。关于物种形成过程的许多理论讨论依赖于从杂交生物那里获得的知识，但许多植物群体都有很高比例的自交受精个体。目前尚不清楚这些近亲繁殖群体是否遵循相同的进化规则，以及它们是否在当地种群中拥有相似数量的遗传变异。通过形态学特征研究的额外数据，学生还将能够确定物种识别的可靠特征，绘制所有分类群的地理分布地图，并评估所有具有可区分特征的群体的正确学名。因此，学生将在广泛的现代系统方法分析植物多样性方面获得宝贵的训练。

Gradute student Morefield under the guidance of Dr. Loren Rieseberg of the Rancho Santa Ana Botanic Garden is studying the several species of an American Southwest sunflower relative, Stylocline, and its relatives, in order to assess levels of genetic and genomic variability within and among populations of these annual and highly inbreeding plants. Primary methods of analysis include protein electrophoresis to sample variation in soluble enzymes extracted from the plants, along with methods of DNA analysis to measure mutational differences in nuclear ribosomal genes and in chloroplast genes. Several related groups of plants also will be studied, in order to construct a phylogenetic framework indicating evolutionary relationships among the species. Much of the theoretical discussion about speciation processes relies upon knowledge acquired from organisms that cross-breed, but many groups of plants include high proportions of self-fertilizing individuals. It is unclear whether these inbreeding groups follow the same evolutionary rules, and whether they harbor similar amounts of genetic variability within local populations. With additional data from studies of morphological features, the student will also be able to determine reliable features for species identification, map geographic distributions for all the taxa, and evaluate the correct scientific names for all those groups with distinguishable characteristics. The student will thus gain valuable training in a broad range of modern systematic methods in the analysis of plant diversity.