DISSERTATION RESEARCH: Drought Tolerance and Evolution of Hydraulic Traits in Juniperus Species

论文研究方向：杜松属植物的耐旱性及其水力性状的进化。本研究旨在阐明系统发育和环境因素对杉树（柏科）抗空泡性和其他水力性状的影响。实施的方法是系统学和生理形态学测量的独特结合。基于DNA序列变异，将构建美国和加勒比地区杜松种的系统发育。生理测量将包括抗空化和水力导电性的水力特性。形态学测量包括木质部导管直径和木材密度。将评估气候、土壤类型、物种和系统发育对水力性状变化的影响。这项研究将在系统学、生理学和生态学的整合上是独一无二的，它将在进化背景下解释物种分布的模式。探索环境和系统发育历史对水生关系中种内和种间变异的影响，将有助于更好地理解适应性状进化和决定植物分布的重要因素。该研究将在生理生态学和植物系统学之间建立新的联系。它还将使土地管理者深入了解入侵北美灌木丛和草原的本土树种的分布控制。

Dissertation Research:Drought tolerance and evolution of hydraulic traits in Juniperus species.Robert B. Jackson and Cynthia J. WillsonDuke UniversityThis study will elucidate the effects of phylogenetic and environmental influences on cavitation resistance and other hydraulic traits in Juniperus (Cupressaceae), a drought-tolerant genus of shrubs and trees. The approach implemented is a unique combination of systematics and physiological and morphological measurements. A phylogeny for juniper species throughout the U. S. and Caribbean will be constructed based on DNA sequence variation. Physiological measurements will include the hydraulic traits of cavitation resistance and hydraulic conductivity. Morphological measurements will include xylem conduit diameter and wood density. The effects of climate, soil type, species, and phylogeny on the variation in hydraulic traits will be assessed. This study will be unique in its integration of systematics, physiology, and ecology to explain patterns of species distribution in an evolutionary context. Exploring the effects of environment and phylogenetic history on variation within and between species in water relations will provide a better understanding of adaptive trait evolution and the factors important in determining plant distributions. This study will forge new links between the disciplines of physiological ecology and plant systematics. It will also lend land managers insight into controls on distribution of native tree species invading into shrublands and grasslands in North America.