PRF/J: Intraspecific Chloroplast-DNA Variation and Phytogeography in the Pacific Northwest

许多植物表现出相似的地理分布，从阿拉斯加东南部到加利福尼亚北部。对三个物种的分子遗传学研究揭示了位于威斯康辛冰川最大值以南的明显的南北细胞质不连续。这些数据表明，冰川作用可能是造成这种不连续性的一个原因，并提出了植物地理学与太平洋西北地区植物遗传结构之间存在联系的可能性。如果是这样，那么其他具有相似地理分布的植物也应该具有相似的遗传变异模式。该研究解决了两个问题：(a)在整个太平洋西北地区的植物分类群中，叶绿体DNA （cpDNA）变异的地理模式是否相似？(b)细胞质和细胞核标记物的变异模式是否一致？采用cpDNA限制性位点分析、rDNA分析和酶电泳技术，对具有不同生活史特征的5个不同分类群（裸子植物、单子叶植物和双子叶植物）进行了研究。从这些数据中，系统发育将被生成，遗传变异的模式将被评估。进一步的分析将解决生物地理学问题，并可能有助于澄清疑似冰川避难所的位置和范围。%%%我们对种内cpDNA变异程度的了解将通过这次调查得到加强。它还将有助于将物种内cpDNA变异的模式和程度与观察到的核遗传标记进行广泛比较，提高对植物遗传结构的认识，并在系统学和群体遗传学领域之间建立重要联系。

Many plants exhibit a similar geographic distribution, occurring from southeastern Alaska to northern California. Molecular genetic investigations of three species have revealed a pronounced north-south cytoplasmic discontinuity located south of the Wisconsin glacial maximum. These data implicate glaciation as a possible causal factor in creating the discontinuity and raises the possibility of a link between phytogeography and the genetic architecture of plants in the Pacific Northwest. If so, then other plants displaying similar geographic distributions should also exhibit similar patterns of genetic variation. This study addresses two questions: (a) do similar geographic patterns of chloroplast DNA (cpDNA) variation occur throughout a spectrum of Pacific Northwest plant taxa?, (b) are patterns of variation in cytoplasmic and nuclear markers congruent? Populations of five taxonomically diverse taxa (a gymnosperm, a monocot, and dicots from Dilleniidae, Rosidae, and Asteridae) having different life history features will be examined using cpDNA restriction site analysis, rDNA analysis, and enzyme electrophoresis. From these data, phylogenies will be generated and patterns of genetic variation will be assessed. Further analysis will address biogeographical questions and may help clarify the location and extent of suspected glacial refugia. %%% Our knowledge of the extent of intraspecific cpDNA variation will be enhanced through this investigation. It will also serve to facilitate a broad comparison of patterns and extent of cpDNA variation within species to that observed for nuclear genetic markers, improve knowledge of plant genetic architecture, and establish an important link between the areas of systematics and population genetics.