Dissertation Research: Systematics and Evolution of the Malagasy Endemic Genus Megistostegium (Malvaceae)

论文研究：马达加斯加特有属Megistostegium（锦葵科）的系统学和进化

• 批准号: 0608444
• 负责人: David Baum
• 金额: $ 1.2万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-15 至 2008-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0608444&HistoricalAwards=false
• 关键词: Dissertation; Research; Systematics; Evolution; Malagasy

The xeric scrublands of southern Madagascar support a number of charismatic and intriguing plant species, more than 90% of which exist nowhere else on earth. The proposed research will focus on the endemic genus Megistostegium and will utilize field and laboratory methods to clarify the evolutionary mechanisms at play in the group's diversification. Prior work has shown that Megistostegium is related to members of the genus Hibiscus that have radiated in arid regions of the island. Megistostegium contains three bird-pollinated species that are morphologically distinct from their close relatives (which appear to be either bird or insect pollinated). A particularly interesting situation occurs at the most southern tip of Madagascar, where all three currently recognized species occur in close physical proximity to each other yet remain morphologically distinct (M. Koopman, pers. obs.). This is intriguing given the fact that these species have overlapping flowering seasons and share the same, single pollinator, a small, green sunbird. There is also one undescribed species of Megistostegium in a remote valley 100 miles to the northeast, which is differentiated by an asymmetrical flower (M. Koopman, pers. obs). The aim of the proposed research will be to explore the genetic relationships, evolution and pollination ecology of Megistostegium. Fieldwork will determine the role of ecological barriers to pollen flow and seek evidence of reproductive barriers after pollination. Leaf tissue will be collected for molecular analyses and sequences for multiple nuclear genes will be produced to elucidate the extent of gene flow between the three forms and whether all three warrant species status (e.g., Is one a hybrid between the other two?). This study will not only enhance basic systematic knowledge of an important group of species in a region threatened by anthropogenic habitat disturbance but has the potential to elucidate the ecological and genetic mechanisms that allow the coexistence of closely related species. Pollination biology at the species and population level has been shown to be of particular importance for the management and conservation of ecosystems. The pollination ecology of a vast majority of African plant taxa remains unexplored and this is especially true on the island of Madagascar. This project will document the pollination ecology of Megistostegium, which will help in planning community level sustainable management of pollinators and the forests they live in. Fieldwork will be conducted with one Malagasy student from the University of Antananarivo, Madagascar and will, thus, facilitate international scientific exchange.

马达加斯加南部的干旱灌木丛养育了许多富有魅力和耐人寻味的植物物种，其中90%以上是地球上其他任何地方都没有的。拟议的研究将侧重于地方性的巨藻属，并将利用田间和实验室方法来阐明在该集团多样化过程中发挥作用的进化机制。先前的工作表明，巨藻与木槿属的成员有亲缘关系，这些成员辐射于该岛的干旱地区。巨藻包含三种鸟类授粉的物种，它们在形态上与它们的近亲(似乎是鸟类授粉或昆虫授粉)截然不同。一个特别有趣的情况发生在马达加斯加的最南端，在那里，目前公认的所有三个物种都在物理上彼此接近，但在形态上仍然截然不同(M.Koopman，PER)。OBS。)。这是耐人寻味的事实，因为这些物种有重叠的花季，并共享相同的单一传粉者，一种小型的绿色太阳鸟。在东北方向100英里的偏远山谷中，还有一种未被描述的巨藻，它的区别在于一朵不对称的花(M.Koopman，Pers)。OBS)。这项研究的目的将是探索巨藻属植物的遗传关系、进化和授粉生态。田野调查将确定生态屏障对花粉流动的作用，并在授粉后寻找生殖屏障的证据。将收集叶片组织进行分子分析，并将产生多个核基因的序列，以阐明三种类型之间的基因流动程度，以及是否所有三种类型都具有可靠的物种地位(例如，其中一种是其他两种之间的杂交？)。这项研究不仅将加强对受到人为栖息地干扰威胁的区域中一组重要物种的基本系统知识，而且有可能阐明允许密切相关物种共存的生态和遗传机制。物种和种群一级的授粉生物学已被证明对生态系统的管理和保护具有特别重要的意义。绝大多数非洲植物类群的授粉生态仍未被探索，在马达加斯加岛上尤其如此。该项目将记录巨型传粉菌的授粉生态，这将有助于规划社区层面对传粉者及其生活的森林的可持续管理。将与马达加斯加塔那那利佛大学的一名马达加斯加学生一起进行实地考察，从而促进国际科学交流。