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

Duke University, Durham NC

Investigators

Abstract

Dissertation Research: Drought tolerance and evolution of hydraulic traits in Juniperus species. Robert B. Jackson and Cynthia J. Willson Duke University This 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.