薜荔-传粉小蜂-Wolbachia遗传结构与比较亲缘地理研究

Distribution and genetic structure of species are deeply impacted by climate oscillations of the Quaternary. Glacial refugia and post-glacial colonization routes of many temperate species have been revealed by phylogeographical studies; however, we still know little about subtropical or tropical species, which, obviously, have also been influenced by climate oscillations. Perennial plants have a long life history and cpDNA variation was accumulated slowly. Thus it is not easy to obtain a clear phylogeographic pattern and correctly infer the glacial refugia and post-glacial colonization routes. The obligate parasites and mutualistic species, which have much shorter life histories, provide ideal proxies for these long-lived species. ..Figs (Ficus, Moraceae) and their pollinating fig wasps form one of the most specific obligate mutualisms. Fig wasps depend on figs to provide larval feeding sites (in galled ovules), while figs depend on fig wasps to transfer pollen between figs. However, fig wasps are frequently infected by the endosymbiont, Wolbachia, which can influence genetic diversity and differentiation of their hosts. ..In the proposed project, an obligate mutualism - Ficus pumila and its pollinating wasps - and Wolbachia of pollinating wasps will be used as the focal system. We will use molecular markers (nDNA microsatellites, and mtDNA, cpDNA, or nDNA sequences) to study genetic structure of F. pumila and its pollinating wasps. We will check infection rate of Wolbachia in pollinating wasps, and study the role of Wolbachia in genetic differentiation of the pollinating wasps. Combining comparative phylogeographic patterns and niche model of F. pumila, we will identify the glacial refugia for these species and their post-glacial colonization routes. The results of this study will provide evidence of impacts on subtropical plants by the Quaternary climate oscillations, and will be useful for predicting the adaptation and changes of specific interactions under prejected climate changes.

物种的分布格局和遗传结构受第四纪冰期的深刻影响，亲缘地理研究已描绘了许多温带物种的第四纪冰期避难所位置及冰期后扩散路线，第四纪温度和(或)降水变化也驱动热带、亚热带物种大范围迁移，但相关研究很少。世代周期较长的多年生植物的叶绿体DNA变异积累较慢，不易追踪这些物种对第四纪气候波动的响应，世代周期较短的强制性寄生或共生的物种可作为代理材料提供精准的信息。本项目拟以强制性共生物种薜荔及其传粉小蜂以及传粉小蜂的内生菌Wolbachia为对象，利用微卫星标记、叶绿体DNA和(或)线粒体DNA标记分析薜荔和传粉小蜂的遗传结构，研究Wolbachia感染对传粉小蜂遗传分化的影响，通过亲缘地理格局比较和生态位模型模拟，确定薜荔-传粉小蜂体系第四纪冰期避难所及冰期后扩散路线，为阐明第四纪冰期对亚热带植物的影响，预测种间关系在气候变化情景下的适应性和变化趋势提供科学依据。

利用分子遗传标记共分析了从82个地点收集的1682个薜荔样本、2094个传粉小蜂样本，经过分析得到如下主要结论：（1）薜荔传粉小蜂已分化为4个不同的物种，分别与台湾海峡形成、武夷山脉抬升、东海海槽等有关，呈异域成种模式。而薜荔世代周期较长，分化为2个变种，也为异域隔离分化；两者分化的差异主要是由于世代周期相差较大。（2）对同域分布的薜荔传粉小蜂出飞物候分析发现，传粉小峰1出飞早于小峰3；基于生境优先占领，小峰1相对小蜂3具竞争优势，因而两者不能稳定共存。（3）利用特异性标记检测，发现所有分析的薜荔传粉小蜂1样本均已感染Wolbachia，而小蜂2、3所有样本均未检测到Wolbachia，符合“全或无”的感染模式，薜荔传粉小蜂物种形成可能与Wolbachia感染无关。（4）根据薜荔的cpDNA和nDNA微卫星标记分析，结合生态位模型分析，显示其冰期避难所大致为1个包含多个小避难所的南方避难所，主体在武夷山-南岭以南；然而传粉小蜂1只分布于武夷山-南岭以北，表明在武夷山-南岭以北肯定至少存在一个冰期避难所，两者比较分析表明，结合紧密相关物种的分析可以获得更为可靠的亲缘地理格局结论。（5）提出了传粉者种群间传粉效率的概念和计算方法，基于不同薜荔传粉小蜂物种大致为异域分布，选择只有一种传粉小蜂分布的华南地区，通过分析薜荔cpDNA和nDNA标记，解析了花粉和种子介导的基因流，利用nDNA微卫星标记分析薜荔小蜂基因流，结合两者世代长度，计算了薜荔传粉小蜂种群间传粉效率为14:1，即大约14个种群间有效扩散的小蜂能够有效扩散1粒薜荔花粉。.结合该项目研究，培养了博士1名、硕士3名。在SCI收录源刊物上发表学术论文7篇，在国际会议上作大会报告1次、口头报告3次。