入侵植物空心莲子草对本地昆虫形成的生态陷阱及其对气候变暖的响应

Exotic invasive plants always form dense monocultures in their new ranges, and attract some native herbivorous insects to feed and oviposite on them resulting in novel associations between them. However, native insects may fail to counter-act the negative impacts of some novel defense traits of their na?ve hosts on their fintess and result in reduced performance.In such cases, exotic plants act as ecological traps for native insect herbivores.In a previous study we have found that a native oligophagous beetle Cassida piperata Hope has shifted its host from native plants to invasive plant A. philoxeroides. The beetle prefers A. philoxeroides over A.sessilis in the field; however, it performs poorer on the exotic host than on the native host indicated by longer larvae duration and lower pupa mass. This result suggests A. philoxeroides may act as an ecological trap for C. piperata, which needs further clarification. Based on this finding and using the beetle's native host A.sessilis as reference, this proposal plan to: 1) further identify the existence of ecological trap and evaluate its impact on the beetle at individual and population level by conducting large-area filed survey, common garden experiments and insect host choice tests; 2) exploit the mechanisms underlying ecological trap including the chemical cues the beetle used to search for host plants and plant defense traits that decreasing beetle fitness; 3) test the impacts of climate warming on the ecological trap and its underlying mechanisms, with simulated warming experiments conducted across a latitudinal gradient. The results of the project will uncover mechanism underlying ecological trap,identify its impacts on native insect and its response to climate warming.Results of this proposal will advance our knowledge of invasion ecology, and will provide valuable information for guiding biological conservation under biological invasion and climate warming scenarios.

外来入侵植物常在入侵地形成大面积的单一优势群落，吸引了本地植食性昆虫。但由于缺乏长期的协同进化关系，入侵植物一些防御机制往往不利于本地昆虫的生长与繁衍，可能成为本地昆虫的生态陷阱(Ecological trap)。本申请项目前期工作发现，我国本地寡食性昆虫虾钳菜披龟甲从其原寄主植物大量转移到入侵植物空心莲子草上，但取食该草后其适合度显著降低。因此，空心莲子草可能成为了该虫的"生态陷阱"。本申请项目拟通过野外调查、同质园和纬度梯度模拟增温实验、室内化学分析及昆虫行为学实验，首先确定空心莲子草对本地昆虫的生态陷阱现象及其对昆虫的影响；然后揭示生态陷阱发生机制；最后，研究气候变暖对生态陷阱的影响及其驱动机理。有关结果将明确空心莲子草生态陷阱机制、生态效应及其对气候变暖的响应，为认识入侵植物的长期生态学影响，以及在生物入侵与全球气候变化背景下保护本地生物多样性提供理论与实践依据。

外来生物入侵严重威胁本土生物多样性，而本土生物亦在外来植物入侵过程中发挥重要调控作用。本项目拟探讨入侵植物空心莲子草与本土昆虫间相互作用、化学生态学机制及对气候变暖的响应。依据项目计划和本领域最新进展，项目组开展了研究并取得以下重要发现：1）空心莲子草、本土植物莲子草与本土昆虫虾钳菜披龟甲在北纬21-36.8度范围内共发生；而引入天敌莲草直胸跳甲目前仅在北纬30.8度以南区域发生。2）在种群水平，空心莲子草对虾钳菜披龟甲无显著影响，并初步发现入侵与本土植物化学物质组成和含量存在差异；3）伴随纬度升高，发生于两种植物上本土昆虫（包括虾钳菜披龟甲）和土壤生物中病原真菌和线虫的种类和数量、引入天敌对本土植物的危害均逐渐降低；4）本土植食性昆虫在低纬度地区显著抑制本土植物莲子草生长，间接促进空心莲子草入侵；在中纬度地区，本土昆虫对入侵与本土植物均无显著作用；而高纬度地区，本土昆虫促进与入侵植物混发的本土植物生长；5）温度升高改变本土植物生活史，提高其春季被地上昆虫危害的风险；但温度升高对入侵植物物候无显著影响；6）伴随纬度升高，土壤生物对本土植物及取食其叶片的植食性昆虫适合度的抑制作用逐渐降低，而对入侵植物无显著影响。上述结果表明：本土地上和地下生物可直接和间接调控入侵植物，且调控作用随纬度而变化；气候变暖可能在发生时间和空间上打破生物间相互作用，影响植物入侵及其危害性。该项目成果已在Ecology Letters、New Phytologist、Biological Invasions、Plant Ecology等杂志发表SCI文章5篇，另有一篇已投稿The ISME J（修改中）。已发表的成果获得F1000专家推荐一次。项目成果为从生物地理学角度剖析外来植物入侵机制、并有针对性的“因地”治理入侵植物提供指导，为气候变化背景下开展传统生物防治天敌筛选提供了指导。但植物作用于昆虫的具体功能性次生代谢物质和化学挥发物，尚待进一步明确。项目组成员参加国际学术会议并作报告3人次，在国内学术会议作报告2人次，1人获得湖北省杰出青年基金资助。