Dissertation Research: A Biosystematic Investigation of the Genus Cornus in the Americas

在导师罗伯特·威尔伯博士的指导下， 杜克大学的研究生扎克·穆雷尔将研究 墨西哥山茱萸的最终目的是提供一个 世界山茱萸属的分类修订 perspective. 实地收集将有助于研究 植物特征的种内和种间变异 结构（整体生长形式），茎色，果实颜色， 栖息地 种子将被收集起来，以便在 a common常见-garden花园environment环境，to examine检查germination发芽requirements要求， 并研究幼苗形态。 收集的材料将 用于扫描电子显微镜研究，染色体 调查、解剖研究和检查 增长的发展模式。 山茱萸属，山茱萸，包括一组 约60种生长在东部温带地区 亚洲、太平洋西北部、北美东部和山区 墨西哥。 尽管所有的山茱萸都有相似的叶子， 花和短柔毛，它们在生长中表现出很大的变化 形态（乔木，灌木和多年生草本植物与木质根茎） 以及植物上花朵的排列， 从开放的分支结构到紧密堆积的头部， 花被艳丽的白色叶子（苞片）包围。 试图 区分物种一直是有争议的， 在深奥的字符的微妙差异。 完成 Murrell的多方面研究将大大改善我们的 了解山茱萸的变异，并为 世界范围的分类学修订。

Under the guidance of faculty adviser Dr. Robert Wilbur, graduate student Zack Murrell of Duke University will study the Mexican species of dogwoods with the ultimate goal of providing a taxonomic revision of the genus Cornus from a worldwide perspective. Field collections will facilitate study of variation within and between species in features of plant architecture (overall growth form), stem color, fruit color, and habitat. Seeds will be collected in order to grow the plants in a common-garden environment, to examine germination requirements, and to study seedling morphology. The collected material will be used in scanning electron microscopy studies, chromosome investigations, anatomical studies, and examination of developmental patterns of growth. The dogwood genus, Cornus, comprises a group of approximately 60 species growing in temperate regions of eastern Asia, Pacific Northwest, eastern North America, and the mountains of Mexico. Although all the dogwoods have similar leaves, flowers, and pubescence, they exhibit great variation in growth forms (trees, shrubs, and perennial herbs with woody rhizomes) and in the arrangement of flowers on the plants, which can vary from an open branched structure to a tightly packed head of flowers surrounded by showy white leaves (bracts). Attempts to distinguish species have been controversial and have had to rely upon subtle differences in recondite characters. Completion of Murrell's multifaceted study will improve greatly our understanding of variation in the dogwoods and set the stage for a worldwide taxonomic revision.