外来植物空心莲子草入侵的土壤微生物学机制及生态学效应

Soil microorganism can influence the competitive relations of native and invasive plants, its impacts on plants could also cascade to aboveground herbivores through food webs indirectly, which result in plant invasion. In previous studies we have found that the soil microbial communities were varied from different soil collection sites, and the direct impact of soil microorganism on native palnt Alternanthera sessilis and invasive plant Alternanthera philoxeroides were differently. In addition, we also found soil biotic effects cascaded to aboveground beetle Agasicles hygrophila performance. These results suggest that soil microbes may regulate the alien plant A.philoxeroides invasion and cause a series of ecological impacts, which needs further clarification. Based on these findings and using the native congeneric plant A.sessilis as reference, this proposal plans to: 1) further identify the soil microbial community structures and functions of different A.philoxeroides invasion area by field survey and lab analysis; 2) exploit the soil microbial mechanisms underlying plant invasion including the plant structure; resource allocation; plant defensive chemicals and insect performance; 3) test the ecological effects of A.philoxeroides invasion mediated by soil microorganisms, with monitoring the fluctuation of A. hygrophila population dynamics and plants competition. The results of this project will uncover mechanism of invasive plant from a novel soil microbial point and identify its ecological effects. Results of this proposal will advance our knowledge of the invasive characteristics and ecological adaptability mechanism of A. philoxeroides, and will provide valuable information for guiding biological control of alligator weed and biological conservation of native species

土壤微生物可以直接影响入侵植物和本地植物的竞争关系，同时其对植物的影响也可以通过食物链对地表昆虫产生级联效应，间接调控外来植物的入侵。申请人前期工作发现，不同分布区土壤微生物群落结构组成各不相同，其对空心莲子草和莲子草适合度的影响各不相同，与植食性昆虫莲草直胸跳甲叶甲存在交互作用，故土壤微生物功能群落可能直接间接或调控了空心莲子草的入侵并产生一系列的生态学效应。本项目拟在现有研究的基础上，通过开展大范围野外调查、植物种植和昆虫饲喂实验、同质园实验，结合分子和化学分析，首先，明确空心莲子草不同分布区地下微生物群落结构组成与功能差异；然后，探讨不同功能群落对空心莲子草入侵的直接间接调控及相关机制；最后，揭示地下微生物功能群介导的空心莲子草入侵的生态学效应。研究结果将从地下微生物功能群落这一全新的角度揭示外来植物入侵机制，为空心莲子草及类似外来入侵植物的生物防治及本地物种保护提供理论和实践指导。

土壤微生物在外来植物入侵进程中发挥着重要作用，也是入侵植物影响入侵地生态系统的重要途径。然而，土壤微生物如何影响入侵植物和本地植物之间的竞争，同时其对植物的影响能否可以通过食物链对地表昆虫产生级联效应，进而间接调控外来植物的入侵，目前尚不清楚。依托该项目，我们对入侵植物空心莲子草和其同属本地植物莲子草根际土壤微生物群落沿纬度梯度进行大范围的野外采样分析，同时进行植物种植和昆虫饲喂实验、同质园实验，结合分子和化学分析研究土壤微生物群落变化对外来植物入侵和地上昆虫的影响。结果发现，由于气候及土壤自身属性差异土壤微生物群落结构呈现纬度梯度变化格局，其中病原真菌沿纬度梯度呈下降趋势，主要归因于较高的土壤pH值。同时，植物种类显著影响土壤共生真菌的群落结构，入侵植物土壤共生真菌的丰度高于本地植物。温室实验和室内分析发现，昆虫取食显著影响空心莲子草土壤真菌丰富度，削弱生防昆虫对莲子草的取食危害，间接促进了空心莲子草的入侵。此外，植物-土壤反馈作用增加了本地植物叶片中蛋白质的含量，抑制入侵植物叶片中总酚的含量，进而使得昆虫在本地植物莲子草上的适合度显著高于在入侵植物空心莲子草上，间接调控了外来植物入侵。本项目研究结果从地下微生物功能群落这一全新的角度揭示外来植物入侵机制，为空心莲子草及类似外来入侵植物的生物防治及本地物种保护提供理论和实践指导。