Dissertation Research: Phylogeny and Speciation in Polygonella (Polygonaceae)

研究生保罗·刘易斯在俄亥俄州立大学丹·克劳福德博士的指导下，将研究美国东南部11种Polygonella属的分类和遗传变异。在冰川融化的更新世冰期之间的温暖时期，这个属中有几个物种似乎进化成了孤立的岛屿种群。在这些时期，佛罗里达半岛被淹没了，除了代表该地区最高陆地块的“岛屿”。例如，两种Polygonella仅限于佛罗里达半岛中心的威尔士湖山脊，其他物种可能已经从这个流行地区分散开来。该研究将通过电泳测定酶变异来检测种内和种间的形态变异以及植物的遗传变异。通过酶电泳检测到的基因特征可能产生有用的数据，用于推断物种之间的进化关系和估计这些植物的育种系统的各个方面，这些系统已知在性别表达上是可变的。因此，Polygonella提供了一个不寻常的机会来调查与更新世岛屿形成有关的过去物种形成事件，这可能会揭示许多佛罗里达特有动植物的起源。

Graduate student Paul Lewis, under the supervision of Dr. Dan Crawford of Ohio State University, will study the taxonomy and genetic variability of 11 species of the genus Polygonella of the southeastern United States. In this genus several species appear to have evolved as isolated island-like populations during the warm periods between Pleistocene ice ages when glaciers melted. The Florida Peninsula was submerged during these times with the exception of "islands" that represented the highest land masses in the area. Two species of Polygonella for example are restricted to the Lake Wales ridge running down the center of the Florida peninsula, and other species may have dispersed from this endemic area. The study will examine morphological variability within and among the species and also genetic variation of plants by measuring enzyme variation using electrophoresis. Gene-characters detected by enzyme electrophoresis are likely to yield data useful for inferring evolutionary relationships among the species and for estimating aspects of breeding systems in these plants, which are known to be variable in sex expression. Thus Polygonella provides an unusual opportunity to investigate past speciation events associated with Pleistocene island formation which may shed light on the origin of many of Florida's endemic plants and animals.