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

马达加斯加南部干旱的灌木丛中生长着许多迷人的植物物种，其中90%以上是地球上其他地方所没有的。拟开展的研究将集中在特有属Megistostegium上，并将利用野外和实验室方法来阐明在该群体多样化中起作用的进化机制。先前的研究表明，Megistostegium与在该岛干旱地区辐射的木槿属成员有关。Megistostegium包含三种鸟类传粉的物种，在形态上不同于它们的近亲（似乎是鸟类或昆虫传粉）。一个特别有趣的情况发生在马达加斯加岛的最南端，在那里，所有三个目前公认的物种在物理上彼此接近，但在形态上却截然不同(M. Koopman, pers。奥林匹克广播服务公司)。考虑到这些物种有重叠的开花季节，并且共享相同的单一传粉者——一种小的绿色太阳鸟，这一点很有趣。在东北100英里的偏远山谷中也有一种未被描述的Megistostegium，其特征是一朵不对称的花(M. Koopman, pers。奥林匹克广播服务公司)。本研究的目的是探讨大穗菊的亲缘关系、进化和传粉生态学。野外考察将确定生态屏障对花粉流动的作用，并寻找授粉后生殖屏障的证据。将收集叶片组织进行分子分析，并产生多个核基因序列，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符合物种地位（例如，其中一种是其他两种之间的杂交品种吗？）该研究不仅可以提高对受人为生境干扰威胁地区重要物种群的基本系统认识，而且有可能阐明近亲物种共存的生态和遗传机制。物种和种群水平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。非洲绝大多数植物类群的授粉生态仍未被探索，在马达加斯加岛尤其如此。该项目将记录巨狐猴的授粉生态，这将有助于规划社区层面对传粉媒介及其生活的森林的可持续管理。实地考察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，从而将促进国际科学交流。

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.