互花米草入侵诱导土著昆虫素毒蛾宿主转移及种群扩增的成因

Invasions by exotic plants can affect insect’s diversity, structure and function of native ecosystems. Studies have shown that native herbivorous insects can transfer or expand their hosts from indigenous plants to invasive plants after the latters have established in the new habitat for many years. There are, however, few mechanisms underlying this phenomenon have been explained. In this project, we want to use "Spartina alterniflora, Phragmites australis and Laelia coenosa” in the Yangtze River estuary as a model system to study that why the indigenous L. coenosa shifts its host from native Phragmites to invasive Spartina in the Yangtze River estuary of China. To address this question, we will compare the differences in physiological (tissue morphologies and nutrition) and habitat characteristics (physical and biological shelters) between Spartina and Phragmites. We are going to conduct the studies under the guidance of principles and methods of population ecology, community ecology and physiological ecology. The research will be, at the first time, focused on the systemic causations for the adaptation of native insects to invasive plants. Our expected outcomes may provide novel sights for understanding the ecological mechanisms underlying the effects of invasive plants on native herbivores, and may also provide references for the habitat restoration and pest management at the wetlands in the invaded regions. The project is expected to publish four papers, among which at least three ones will be published in SCI journals (including one in the top journals of ecology).

植物入侵以多种不同方式影响土著生态系统中昆虫的多样性、结构及功能。现有研究发现，随着入侵植物在新生境中定殖时间的延长，土著植食性昆虫可发生食性转移或扩大，从而较好地适应这些外来新宿主；但是，对这一现象背后的成因，仍需进一步强化系统的科学认识。本项目拟以长江河口的“互花米草–芦苇–素毒蛾”为研究系统，通过比较外来植物互花米草和土著植物芦苇的生理性状（聚焦于形态组织和营养指标）和生境特征（聚焦于物理庇护和天敌庇护）为素毒蛾提供生存繁衍的异同效应这一角度，分析互花米草入侵促进土著昆虫素毒蛾宿主转移和种群扩增的主要成因。可望通过本项目的实施，在外来植物入侵与土著昆虫食性微进化关系这一研究方向内取得创新成果，为植物入侵对土著昆虫影响的生态学机制提供新的认识，为被入侵生态系统的生境恢复和湿地植物害虫的综合治理提供参考。本项目预期发表论文4篇，其中SCI论文不少于3篇（争取1篇在生态学顶尖刊物发表）。

植物入侵以多种不同方式影响土著昆虫的多样性和种群发展。现有研究发现，随着入侵植物在新生境中定殖时间的延长，土著广食性昆虫可发生宿主转移而较好地利用入侵植物；但是，对这一现象的成因及昆虫种群的响应后果仍需进一步强化系统认识。本项目以长江口的“入侵植物互花米草–土著植物芦苇–土著广食性昆虫素毒蛾”为研究系统，通过比较互花米草和芦苇的生境特征、生理性状等差异，分析了植物入侵对土著昆虫种群发展的影响与成因。主要结果如下：.（1）发现在长江口盐沼中，互花米草相对于芦苇具有更长的生长期、更广的分布面积、更高的生物量，且生境中昆虫天敌数量较少，诱导了素毒蛾种群向入侵生境转移，证实了资源可利用性（Resource availability）和无天敌空间（Enemy-free space）在入侵植物–土著昆虫互作中的促进作用。（2）发现互花米草群落中诱导素毒蛾繁殖的环境线索（资源可用性和叶气味）和决定昆虫种群适合度的资源质量（营养和防御）之间存在不匹配性，导致土著昆虫陷入入侵的“生态陷阱”。（3）发现素毒蛾取食诱导了互花米草防御性状呈高抗性、低耐受性的进化模式，表明引入地广食性昆虫取食压同样可导致入侵植物引种后发生防御的快速进化，但抗性和耐受性两种防御性状存在“权衡（trade-off）”关系。.以上结果表明，土著广食性昆虫拓展利用入侵植物互花米草，是由入侵植物给土著昆虫所提供生境条件和可利用资源的共同影响所决定的。当前状态下，由于互花米草给土著昆虫所供资源的数量与质量性状之间存在“退耦性（decoupling）”，对土著昆虫总体上存在负面影响。虽然如此，昆虫的取食压力已导致入侵植物抗虫性发生了增强性进化。本项目增强了我们对入侵植物–土著昆虫相互作用关系的深刻认识，未来需进一步探索土著昆虫能否通过进化调整快速适应入侵植物。