Phylogenetic Systematics and Biogeography of Asclepias

[04:15213 . 13]乳草是北美温带地区著名的开花植物。它们已被传粉生物学家、进化生物学家和化学生态学家广泛研究，并作为植物-昆虫共同进化研究的模型系统。乳草是黑脉金斑蝶最著名的寄主植物——乳草产生的心糖苷被黑脉金斑蝶隔离，用来对抗鸟类捕食者，这一发现是进化生态学的一个经典进展。然而，对乳草种间关系的研究远远落后于乳草种群生物学和化学研究的巨大进展。通过对马利筋物种间系统发育关系的研究，我们可以更深入地了解已经得到充分研究的生态和进化过程，并评估这些现象的普遍性。密西西比州立大学的Mark Fishbein博士的研究将改进马利筋属（Asclepias）的分类，分析过去和现在的杂交，并阐明北美和非洲物种之间的生物地理联系。推断出的Asclepias的系统发育将被用作回答几个关键的进化和生物地理问题的框架：1)所有的美洲乳草都来自一个非洲殖民者，还是美洲物种中有几个祖先非洲血统？(2)乳草是经由北大西洋到达北美洲还是经由南美洲？3)是否有证据表明，在形态完全不同的物种之间存在过去的杂交和渐渗，而这些物种不再能够杂交？阐明Asclepias的进化史将对一个产生了无处不在的杂草和北美一些最稀有物种的群体提供重要的见解。这也将为未来研究乳草及其专门的昆虫食草动物的共同进化提供重要的基础。这个项目的结果可能会影响到系统学、进化论和生态学以外的学科。乳草越来越多地被用于园艺，作为园林多年生植物和切花。增加对乳草关系的了解将通过确定可使用既定方案种植的栽培物种的近亲来促进新园艺材料的开发。以乳草为基础的植物化学研究将得到加强，特别是针对农药开发的研究。由于Asclepias是黑脉金斑蝶的主要寄主植物，该项目将有助于保护受威胁的黑脉金斑蝶种群。墨西哥同事Zamudio Ruiz和英国同事d.j. Goyder的实地和实验室工作将加强国际合作。此外，PI正在开发马利筋作为了解物种间杂交如何发生的模型系统，这对于理解转基因生物的生态影响至关重要。该项目将对分子系统学和进化生物学的研究生和本科生培训产生重大影响。密西西比州立大学提供了一个极好的机会，以增加在生物科学中代表性不足的群体的研究机会。学生们将在区域和国家会议上展示他们的研究成果。

0415213Fishbein Milkweeds are well known flowering plants of temperate North America. They have been widely studied by pollination biologists, evolutionary biologists, and chemical ecologists, and have served as a model system in studies of plant-insect coevolution. They are perhaps best known as the host plant of the Monarch butterfly - the discovery of the role of cardiac glycosides produced by milkweeds and sequestered by Monarchs for use against avian predators was a classic development in evolutionary ecology. However, research on milkweed species relationships has lagged far behind the tremendous progress in studies of the population biology and chemistry of milkweeds. A much deeper understanding of well-studied ecological and evolutionary processes and the ability to assess the generality of these phenomena will be gained from this investigation of the phylogenetic relationships among milkweed species. Research by Dr. Mark Fishbein at Mississippi State University will result in an improved classification of the milkweed genus (Asclepias), analyses of past and current hybridization, and elucidation of the biogeographic link between North American and African species. The inferred phylogeny of Asclepias will be used as a framework for answering several key evolutionary and biogeographic questions: 1) Are all American milkweeds derived from a single African colonist, or are several ancestrally African lineages represented among the American species?, 2) Did milkweeds arrive in North America via a North Atlantic crossing or via South America?, and 3) Is there evidence for past hybridization and introgression between morphologically disparate species that are no longer capable of hybridization? Elucidating the evolutionary history of Asclepias will give important insights into a group that has given rise to ubiquitous weeds and some of the rarest species in North America. It also will provide a crucial basis for future studies of the coevolution of milkweeds and their specialist insect herbivores. The results of this project will likely impact disciplines beyond systematics, evolution, and ecology. Milkweeds are increasingly being used in horticulture as garden perennials and cut flowers. Increased understanding of milkweed relationships will foster development of new horticultural materials by identifying close relatives of cultivated species that can be grown using established protocols. Studies of plant chemistry based on milkweeds will be enhanced, especially research targeting pesticide development. Because of the importance of Asclepias species as the primary host plant of the Monarch butterfly, this project will contribute to the conservation of threatened Monarch butterfly populations. Field and laboratory work with Mexican colleague Zamudio Ruiz and British colleague D. J. Goyder will enhance international collaboration. In addition, the PI is developing milkweed as a model system for understanding how hybridization occurs between species, which is critical for understanding the ecological impacts of genetically modified organisms. This project will significantly impact graduate and undergraduate training in molecular systematics and evolutionary biology. Mississippi State University provides an excellent opportunity to increase the research opportunities of underrepresented groups in biological sciences. Students will present the results of their research at regional and national meetings.