飞机草入侵种群天敌防御策略的进化及对其成功入侵的贡献

Biological invasions are one of the major threats to the biodiversity and ecosystem functioning in receiving communities. It has resulted in serious environmental and socioeconomic problems and has become one of the hottest topics in current ecology research. In the introduced ranges, alien invasive plants escaped from the damages of specialists, but may experience the same or even higher level of damages from generalists. Invasive plants may evolve in response to the altered enemy regime by increasing their defences (including resistance and tolerance) against generalist’s damages. However, whether invasive species will benefits from the increased defences when competing with their co-occurring native plants in the invading communities are not well elucidated. Chromolaena odorata is a noxious invasive species in the tropic and subtropics and one of the worst invasive alien plant species in China. By using plants from invasive, native source populations of C. odorata and co-occurring native species within the invading communities, we will compare the differences in generalist defence ability, the costs of defence ability and competitive ability of plants from different population or species we hypothesize that: comparing to plants from native source populations and co-occurring native plants, invasive C. odorata plants will evolve in response to altered enemy regimes, and: 1) have higher generalist defence ability due to low costs of generalist defences. 2) have higher competitive ability due to lower costs of tolerance, especially when invasive C. odorata plants competing with co-occurring native plants under herbivore damages. 3) allelopathic effect further improve the performance of invasive plants over co-occurring native plants when competing against each other. Results of this research can shed some lights on the mechanisms of plant invasions. Besides, it can improve our knowledge in managing and alleviating the negative impacts of invasive C. odorata plants.

生物入侵严重危害入侵生态系统结构和功能，是严重的环境和社会经济问题，也是生态学研究的热点之一。在入侵地，入侵植物逃离了专性天敌的危害，但广谱性天敌的危害可能不变甚至更高。入侵植物天敌防御（抗性和耐性）可能对天敌组成变化进化响应，使其广谱天敌防御能力不变甚至更高。然而，目前还很少研究验证天敌防御策略的进化及其对外来植物入侵成功的贡献。本项目拟以外来入侵植物飞机草入侵地种群及其原产地源种群和入侵种群共存的本地种为材料，通过比较不同类群植株的广谱天敌抗性、耐性及成本差异，结合竞争实验，探讨飞机草入侵地种群与原产地源种群相比，是否对天敌组成变化做出进化响应：有更高的低成本的广谱天敌防御能力；高的天敌耐性使其与本地种在遭受天敌危害时竞争优势更加明显；化感作用进一步有利于其与本地种的竞争。通过本项目的研究，不仅能够丰富和完善现有的入侵生态学理论，同时有助于人们对外来种进行科学管理与防治。

在入侵地，入侵植物逃离了原产地专性天敌的危害，但广谱性天敌、人类干扰等危害水平可能不变甚至更高。入侵植物可能对原产地与入侵地天敌、人类干扰危害差异适应，使其广谱性天敌、干扰危害的防御能力（抗性和耐性）不变甚至更高。通过对云南省5个地点的飞机草入侵程度不同的样方进行调查，比较了飞机草入侵程度不同样方的土壤养分、群落结构、飞机草与本地种天敌危害差异。基于野外调查结果，在同质种植园内比较了飞机草及6种常见的伴生本地种对不同程度人工去叶（模拟天敌、干扰危害）处理响应差异。随后，在同质种植园内开展了3个竞争实验，分别比较了墨西哥和中国的本地种群落、刈割、飞机草种群（遗传）多样性对其入侵成功的影响。研究发现，与飞机草轻度入侵样方相比，严重入侵样方内土壤总碳、总氮、水解性氮含量显著更低，而中度入侵样方土壤有效磷含量则明显更高；中度入侵和严重入侵样方内物种多样性明显更低、严重入侵样方内植株密度、盖度显著更低；严重入侵样方内植株天敌危害频率明显更低；所有样方内，飞机草被取食面积明显低于伴生的本地种。与对照相比，去叶75%处理显著降低了本地种总生物量（除蔗茅外）；去叶处理对飞机草总生物量无显著影响，表现对去叶处理有完全补偿的能力。与墨西哥本地种群落相比，中国的本地种群落更容易被入侵；刈割能进一步增加飞机草的入侵优势，其对中国本地种群落可入侵性增加更加明显。与入侵地本地种标准人工群落竞争时，飞机草入侵地植株较原产地植株有更高的竞争力；群落内飞机草种群（遗传）多样性增加并未增加其与本地种群落竞争时的优势，表明群落内飞机草的遗传多样性水平与其入侵能力可能并不存在直接的关联。通过本项目的实施，对飞机草入侵成功的机制有了更深的了解，同时，可为飞机草防治提供指导和理论依据。