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

马达加斯加南部的干旱灌木丛支持许多魅力和迷人的植物物种，其中90%以上在地球上其他地方都不存在。拟议的研究将集中在特有属Megistostegium，并将利用现场和实验室的方法来澄清在该组的多样化发挥作用的进化机制。先前的工作表明，Megistostegium与在该岛干旱地区辐射的木槿属成员有关。巨冠菊属包含三种鸟类授粉的物种，在形态上与它们的近亲（似乎是鸟类或昆虫授粉）不同。一个特别有趣的情况发生在马达加斯加岛的最南端，所有三个目前公认的物种发生在物理上彼此接近，但形态上仍然不同（M。Koopman，pers. obs.）.这是有趣的，因为这些物种有重叠的开花季节，并共享相同的，单一的传粉者，一个小的，绿色太阳鸟。在东北方100英里的一个偏远山谷中，也有一种未描述的巨冠菊属物种，它由一种不对称的花（M。Koopman，pers. obs）.本研究旨在探讨巨冠属植物的亲缘关系、进化和传粉生态学。实地考察将确定生态障碍对花粉流动的作用，并寻找授粉后生殖障碍的证据。将收集叶组织用于分子分析，并将产生多个核基因的序列，以阐明三种形式之间的基因流动程度以及所有三种形式是否保证物种地位（例如，两者之间有一个是混合体吗？）。这项研究不仅将提高一个重要的物种在一个地区的人类活动的栖息地干扰威胁的基本系统的知识，但有可能阐明生态和遗传机制，使密切相关的物种共存。在物种和种群水平上的花粉生物学已被证明对生态系统的管理和保护特别重要。绝大多数非洲植物类群的授粉生态学仍然没有被探索，这在马达加斯加岛上尤其如此。该项目将记录Megistostegium的授粉生态学，这将有助于规划社区一级的可持续管理授粉者和他们生活的森林。将与马达加斯加塔那那利佛大学的一名马达加斯加学生进行实地考察，从而促进国际科学交流。

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.