Phylogenetic Relationships in Dioscorea, The True Yams

美国纽约州立大学石溪分校的Geeta Bharathan获得了一项研究基金，用于研究薯蓣（真正的山药）的进化关系。薯蓣是一个大的，经济上重要的单子叶属，包含大约600种，大多数热带，生长在一系列栖息地的藤蔓。尽管薯蓣作为块茎和药用作物的传统价值（以及最近在制药业的价值），薯蓣的分类却混乱不堪。100多年前，著名的分类学家胡克发表声明说：“……“薯蓣属的物种正处于一种难以形容的混乱状态”这一问题正通过许多一级分类学家的英勇努力慢慢得到纠正，但更高层次的关系问题是一个棘手的问题，仅靠传统的形态学方法可能无法解决。在本项目中，将对世界各地的薯蓣物种进行取样，以研究其分子（三个基因的DNA序列）和形态（野外和植物标本室收集的观察）的变化。分子序列将进行分析，以制定进化关系的假设，并为该组构建一个系统框架。这将有助于实现以下几个目标：1)评估以前的分类，以便于分类修订；2)评估特定亚群的进化基础（例如，包括三个北美物种的亚群），以帮助了解这一大属的历史起源和生物地理分布；3)形态性状评价，提高其在属分类中的应用；4)编制用于系统发育分析的形态数据集，与世界各地的薯蓣科学家合作完成。实现上述目标的更广泛意义具有科学和社会两个方面。该项目将产生一个严格的系统框架，然后可用于研究这种重要热带作物的各个方面：营养形态和发育（包括叶片形态和结核形成）的进化、多样化的生物地理模式和驯化的历史。所有这些都将有助于作物的未来利用和改良。该项目将使学生（研究生和本科生）能够在包括形态学在内的实地和实验室方法方面得到培训，同时使他们了解收集和利用其他国家种质资源所涉及的重要国际问题。该项目有一个墨西哥合作者明确参与，利用地理信息系统进行植物收集和制图，并由PI在墨西哥教授一门关于系统发育的课程。所有这些活动将有助于建立1)关于一种重要但尚未得到充分研究的热带作物的科学知识基础；2)国家和国际一级的科学技能和基础设施；3)国际合作和科学交流。

ABSTRACTA grant has been awarded to Geeta Bharathan at SUNY at Stony Brook to study the evolutionary relationships of Dioscorea (the true yams). Dioscorea is a large, economically important monocot genus that contains about 600 species of, mostly tropical, vines that grow in a range of habitats. Despite its traditional value as a tuber and medicinal crop (and, recently, in the pharmaceutical industry) the taxonomy of Dioscorea is in a mess. While a statement, over a 100 years ago, by the famous taxonomist, Hooker, that "...the species of Dioscorea are in a state of indescribable confusion" is slowly being remedied through heroic efforts by a great many alpha-taxonomists, the question of higher level relationships is a thorny one that traditional morphological approaches alone may not be able to resolve. In this project species of Dioscorea across the world will be sampled to study variation in molecules (DNA sequences of three genes) and morphology (observations on field and herbarium collections). Molecular sequences will be analyzed to formulate hypotheses of evolutionary relationships and to construct a systematic framework for the group. This will help to achieve several goals: 1) Evaluation of previous classifications to facilitate taxonomic revisions; 2) Evaluation of the evolutionary basis for particular subgroups (e.g., the one that includes the three North American species) to help understand the historical origins and biogeographical spread of this large genus; 3) Evaluation of morphological traits to improve their use in classification of the genus; 4) Compilation of a morphological data set for phylogenetic analysis, to be done in collaboration with Dioscorea scientists across the world.The wider significance of the achievement of the above objective has both scientific and societal aspects. The project would generate a rigorous systematic framework that then can be used to study various aspects of this important tropical crop: evolution of vegetative form and development (including leaf form and tuber-formation), biogeographical patterns of diversification, and history of domestication. All these would contribute to future uses and improvement of the crop. The project would enable training of students (graduate and undergraduate) in field and laboratory methods including morphology, while at the same time exposing them to important international issues involved in the collection and utilization of germplasm from other nations. The project has the explicit involvement of a Mexican collaborator for plant collection and mapping using GIS, and a course on phylogenetics to be taught in Mexico by the PI. All these activities will contribute to building 1) a scientific base of knowledge on an important, but understudied, tropical crop, 2) scientific skills and infrastructure at the national and international levels, and 3) international collaboration and scientific exchange.