以专性传粉者介导的同域榕属物种间的生殖隔离机制

Reproductive isolation is the basal factor for species to keep integrity and independence, whereas pollinating insects are important to govern the formation and maintenance of reproductive isolation among plant species. Figs (Ficus spp., Moraceae) and their pollinating fig wasps (Hymenoptera, Agaonidae, Chalcidoidea) constitute a classic example of an obligate plant-pollinator mutualism depending on the chemical barriers (flower develoments and species-specific odour) and physical ones (ostiolar diameter and style length), and have become an ideal system for addressing questions on coevolution, speciation, and maintenance of mutualisms. Traditionally, it was thought that each fig species had its own species-specific fig wasp, and the fig-fig wasp mutualism was a classic example of the strict-sense co-speciation based on tightly coevolution. However, more and more findings of fig wasp co-ocurrance and fig hybridization challenged species co-speciation and imply that reproductive isolation among figs is not thorough. So the mutualisms are more sophisticated than we had thought.. In this project, at the base of our present work we will focus on all the figs in the permanent sample plot of 20 ha area belong to Dinghushan National Nature Researve, and study their reproductive isolation using phytochemical analysis, morphology and action observation, phenology and phylogenetic analysis. Using gene sequencing and microsatellites, we will compare the occurrence of hybridization and co-pollinator between monoecious and dioecious figs, among different clades of the phylogenetic tree. Thus to better understand how the congeneric species in sympatry keep reproductive isolation, and provide solid evidence to the biodiversity theory.

生殖隔离是物种得以保持完整性和独立性的基础,而传粉昆虫对植物种间生殖隔离的形成与维持具有重要作用。榕与榕小蜂组成迄今为止所知道的联系最密切的高度专性共生体系，并由化学障碍（花发育期和宿主特有的挥发性气味）和物理障碍（花序口直径和花柱长度）来共同维持物种间的生殖隔离。但大量传粉者共存及榕树杂交渐渗的发现，使我们对榕-榕小蜂“一对一”共生及物种间“严格执行生殖隔离”的观点发生改变，这个系统也变得更为复杂。. 因此，本项目拟在已有工作基础上，以鼎湖山20公顷样地内所有榕树为研究对象，采用植化分析、形态行为观察、物候观测、系统发育分析等方法，明确榕树物种间的生殖隔离机制；并利用分子生物学方法检测杂交渐渗及传粉者共存在榕树不同繁育系统、不同进化支系中的发生情况。从而为同域分布的同属物种间如何保持生殖隔离、维持生物多样性提供实证。

生殖隔离是物种得以保持完整性和独立性的基础,而传粉昆虫对植物种间生殖隔离的形成与维持具有重要作用。但大量传粉者共存及榕树杂交渐渗的发现，使我们对榕-榕小蜂“一对一”共生及物种间“严格执行生殖隔离”的观点发生改变，这个系统也变得更为复杂。为此，我们对同域和异域榕树及其传粉榕小蜂的共享和种间隔离机制进行研究。..主要研究内容和重要结果有：.1..以鼎湖山样地和华南植物园内榕树物种为研究对象，采用植化分析、昆虫行为观察、 花序形态和开花物候观测、系统发育分析等多方面的技术和手段，明确榕树物种间的生殖隔离机制主要是接收期花序气味、花序及传粉小蜂形态互适和花序物候综合作用的结果；.2..SSR分子标记方法表明同域榕树物种间较少杂交和基因渐渗，且榕树物种间传粉蜂虽存在共享，但比例较低，且多是在近缘榕树物种间发生；.3..此外，本项目组还对不同地理区域榕小蜂共享和物种分化情况进行了多重比较研究，提出传粉蜂共享比例在近缘榕树物种间存在差异，且共生榕小蜂形态会虽宿主榕树形态变异而发生适应性进化；.4..对榕小蜂嗅觉相关基因进行初步研究。.5..把榕小蜂线粒体COI和核基因ITS序列上传到genebank。..研究意义：.为同域分布的同属物种间如何保持生殖隔离、维持生物多样性提供实证，有助于理解协同进化机制和物种多样性形成。