不同生态型外来种喜旱莲子草在大气CO2升高下的扩散潜能和生物控制

Alternanthera philoxeroides, which originated in South America, is a noxious weed species in the warm temperate and subtropical regions of China, infesting most kinds of water bodies and many terrestrial habitats. A host-specific flea beetle, Agasicles hygrophila, introduced from the USA in 1986 as a biological control agent, has become widely established in South China and has effectively controlled the weed in many water bodies. However, the nitrogen content, degree of lignification and secondary metabolites levels in different ecotypes of the plant always influence the ingestive behavior and population dynamics of the beetles. It has been observed, therefore, that the beetle's ability in controlling the weed in terrestrial habitats has been limited..With the ongoing increase in atmospheric CO2, it is necessary to study comprehensively and continuously effects of elevated CO2 on plant invasion and its biological control in the future. The Open Top Chamber (OTC) system is adopted in the project to study the effect of elevated CO2 on morphological structure, physiological adaptability and chemical components of xerophytic and aquatic Alternanthera philoxeroides. Whether these variations promote its Competitive advantage and benefit for its spread ability? The trend analysis of biological control of the invasive plant and the interspecfic relationship of plant and bettle are the key researches in the project. The innovations of this work are integrating the effects of increasing CO2 and other aspects of global change on plant invasion, implications for prediction and control of invasive plants in the future.

世界恶性外来种喜旱莲子草具有多种生态型。利用专一性天敌莲草直胸跳甲能成功防治该物种水生型，但植株叶氮含量、木质化结构以及次生代谢产物均显著影响天敌的摄食与种群增长，从而导致旱生型植株无法有效控制。由于该物种植株在不同生态型之间的转变非常迅速，所以水体生态系统的侵入威胁依然存在。本项目采用OTC控制系统研究未来大气CO2浓度升高对水生、旱生型植株形态结构、生理适应、化学成分等的影响，并分析这些变化是否加剧该物种的扩散。重点考察各生态型植株形态、成分的改变是否有利于天敌对其生物控制，建立气候变化下喜旱莲子草- - 直胸跳甲之间的种间关系模型。本项目的实施将气候变化和外来种入侵与防治两大全球问题结合研究，在已有的工作基础上，为入侵种未来的扩散和防治作出科学的评估和预警。在众多类似的全球变化研究中，本工作最大的创新性在于探索不同生态型喜旱莲子草在未来气候变化中的生物控制趋势及关键因素。