地果种群分化与其专性共生传粉小蜂的协同进化关系研究

Population divergence and speciation are among the essential topics of evolutionary biology. The species with restricted dispersal abilities might diverge on a small geograhic scale responding to the heterogeneity of habitats. It was suggested by theoritical researches that coevoltuion between highly depended species would enhance population divergence and the speciation processes. However, it was controversial about the role of coevolution on population divergence in the specific mutualism systems. Ficus tikoua distributes widely in the ecotone between Tibetan Plateau and Sichuan Basin where environmental conditions change sharply. Ficus tikoua and its specific pollinating fig wasp depended on each other for reproduction, and are among the most tightly coevolved plant-insect mutualisms. Ficus tikoua is a functionally dioecious prostrate shrub with figs partially buried in the soil which restricts the dispersal distance of itself and also the pollinating fig wasps seriously. Our preliminary study on six F. tikoua populations revealed obvious genetic differences between Sichuan Basin and Hengduan Mountain populations, which was inconsistent with the pattern of widespread species. To explore the coevolution dynamics between F. tikoua and its specific pollinator and their response to environmental changes, we planed to employ nuclear microsatellite, exon-primed- intron-crossing loci, chloroplast and mitochondrial genes to scan the genetic variations of their populations. The relationships between the population genetic structure of host and pollinator, and between the genetic structure and habitats will be tested. The species specificity between host and pollinator will be assessed. Typical F. tikoua populations in different habitat will be chose for ecological and phenological survey. Then mature male and female trees from each chosen populations will be transplanted into the same garden, and the stabilities of their ecological and phenological characters will be assessed by investigation and pollinator introduction for at least two years. The results will help to predict the responses of highly depended fig and fig wasp to environmental changes, and to explore the underlying mechanism shaping the amazing biodiversity in the ecotone between Tibetan Plateau and Sichuan Basin.

种群和物种分化是进化生物学的核心问题之一，低迁移能力物种可在较小空间尺度上响应环境变化而分化。理论研究预测相互作用物种的协同进化可促进分化，但专性共生体系中协同进化对种群分化的作用却备受争议。地果为青藏高原-四川盆地生态过渡带的乡土种，与其传粉小蜂专一性共生；铺地藤本的生活型决定地果及其传粉小蜂的扩散能力相当有限。我们的前期研究揭示四川盆地和横断山区的地果种群有明显遗传分化，为探讨地果-传粉小蜂的分化与协同进化动态及其对生境变化的响应，我们拟调查不同生境典型地果种群的生态特征、繁殖物候，同质园栽培验证地果生态特征及与传粉小蜂共生动态的稳定性；采用nSSR/EPIC、cpDNA、mtDNA分子标记，分析地果-传粉小蜂的种群遗传分化格局及与生境的相关性，检验两者遗传格局的一致性和协同关系，为探讨专性共生物种对环境变化的响应提供科学依据，为解读我国青藏高原-四川盆地生物多样性形成机理提供参考。

种群与物种的分化是进化生物学的核心问题之一，紧密联系物种间的相互作用被认为是生物多样性形成的重要驱动力，但性共生体系中协同进化对种群分化的作用却备受争议。本项目利用低扩散能力的地果与地果传粉小蜂探讨专性共生物种对青藏高原东缘环境快速变化的响应。项目组观察了地果的物候、分析了四川盆地、横断山脉及云贵高原的51个地果与地果传粉小蜂种群的遗传格局及其相互关系、比较了地果与地果传粉小蜂相互作用关键性状的分化与对应关系、探讨了地理隔离与环境条件对地果及其传粉小蜂分化的作用。结果显示地果与地果传粉小蜂均呈现出对环境条件的适应性分化，物候表现出对亚热带季节性气候的趋同适应；地果的传粉关键性状(雄花分布位置、花药胚珠比)已产生稳定分化，云贵高于与四川盆地-横断山区之间表现出显著差异，但地果传粉小蜂的关键性状(花粉筐、花粉刷)却未显示出对应的分化；地果与地果传粉小蜂已有明显的遗传分化，两者的种群分化、遗传格局均高度对应，呈现出群组的协同分化；区域尺度的基因流地理障碍、小尺度的距离隔离在地果与地果传粉小蜂的种群分化和遗传格局的形成中起到重要作用。项目成果将为探讨专性共生物种对环境变化的协同响应提供可靠的案例、为解读我国青藏高原-横断山脉-四川盆地生物多样性的形成机理提供参考。.项目组发表第一标注科研论文6篇，第二标注论文2篇，8篇均为SCI收录论文；项目执行期间培养硕士研究生4人。