Dissertation Research: Systematics of An Old Polyploid Complex in the Genus Gaudichaudia (Malpighiaceae)

在教师顾问威廉·安德森博士的指导下，密歇根大学的研究生史蒂文·杰赛普正在研究马拉科植物高迪乔迪亚属植物，这是美洲热带地区的一组开花藤本植物。这一组中的物种表现出几种不同水平的染色体加倍，称为多倍体，以及几种明显的形态分离谱系之间的杂交实例，导致不育和可育的中间体。多倍体在远亲血统之间产生可育的杂交后代的能力，以及来自不同祖先的多倍体杂交然后回交到亲本四倍体的能力，导致了一系列遗传复杂的形式，其中物种之间清晰的形态边界被模糊。通过使用DNA限制性片段标记和蛋白质电泳，结合标准的分类学方法，研究人员将识别和表征物种，并根据地理范围和土壤/气候分布分析生态小种。利用计算机辅助的系统发育分析方法，他们将推断该属的分类群的起源和进化历史，并检验该类群通过杂交表现出物种形成的多倍体循环模式的假设。多倍体周期很少受到关注，特别是在热带木本植物中，但高染色体数量的出现表明热带类群中存在广泛的多倍体进化。正在使用的新的分子方法有望突破我们对多倍体进化的普遍和意义的理解。

With guidance from faculty adviser Dr. William Anderson, graduate student Steven Jessup of the University of Michigan is studying plants of the genus Gaudichaudia of the Malpighiaceae family, a group of flowering vines of the American tropics. Species in this group exhibit several different levels of chromosome doubling, called polyploidy, along with several apparent instances of hybridization between morphologically separate lineages, leading to both sterile and fertile intermediates. The ability of polyploids to produce fertile hybrids between distantly related lineages, and for polyploid hybrids from different progenitors to cross and then backcross to parental tetraploids, results in a genetically complex array of forms where clear morphological boundaries between species are blurred. By using DNA restriction fragment markers and protein electrophoresis in combination with standard taxonomic methods, the researchers will identify and characterize species, and analyze ecological races in terms of geographic range and soil/climate distributions. Using computer-aided methods of phylogenetic analysis, they will infer the origins and evolutionary history of taxa in this genus, and test the hypothesis that the group exhibits a pattern of polyploid cycles of speciation through hybridization. Polyploid cycles have received little attention, especially in tropical woody plants, yet the incidence of high chromosome numbers suggests extensive polyploid evolution in tropical taxa. The new molecular methods in use promise a breakthrough in our understanding of the prevalence and significance of polyploid evolution.