天敌逃逸对木本植物负密度制约效应的影响：生物过程与机制

Understanding species coexistence and the maintenance of biodiversity has long been the central interest of ecologists. Negative density dependent effect (Janzen-Connell hypothesis) is one of the important theories of plant community composition. Enemies (e.g. herbivores or pathogens) damaged on plants and resource competition are the two reasons of negative density dependent effect occurs. An.understanding of the relative importance of different natural enemy types is limited, as research that has tested the impacts of certain enemy types individually is poorly equipped to assess which natural enemy types contribute most to this diversity-promoting mechanism. Exotic tree species could invade one region into new areas, with biotic and abiotic factors changing, and these factors are the main reason of negative density dependent effects. In order to test whether invasive tree Triadica could escape density dependent effect when introduced to US from China, and examine which classes of enemies determine theses phenomenon. We performed field investigation, two reciprocal shade-house.(greenhouse) experiments, and two field common garden experiments in which we grew Triadica from native and introduced populations under soil treatments between native and introduced ranges. The results are helpful to reveal the relative importance of different types of natural enemies in the negative density dependent effect, and clarify the mechanisms of woody plant species invasion success and develop reasonable and effective biological control measures.

物种共存和生物多样性维持一直是生态学研究的中心论题。负密度制约(也称Janzen-Connell假说)是影响植物群落物种组成的重要理论之一。有害生物(如：食草动物和病原微生物)对植物体的侵害和资源竞争是导致负密度制约效应发生的两大主要原因。区别不同类型的有害生物在负密度制约效应中的相对重要性是是近年来研究的一个热点和难点问题。入侵性木本植物从一个区域引入到新的区域后，生物因子和非生物环境发生了改变，而这些因子是导致入侵性树种在原产地发生负密度制约效应的原因。本项目拟以多年生木木植物乌桕为研究对象，在乌桕的原产地中国和入侵地美国，采用野外调查、野外同质园、室内控制试验的实验手段，研究乌桕从中国入侵到美国后，天敌的逃逸是否使乌桕逃离了负密度制约效应的限制。研究结果有助于揭示不同类别的天敌在负密度制约效应中的相对重要性，并对阐明木本植物的入侵机制以及开展合理有效的生物防治措施有

物种共存和生物多样性维持一直是生态学研究的核心问题。负密度制约(也称Janzen-Connell假说)是影响植物群落物种组成的重要理论之一。有害生物(如：食草动物和病原微生物)对植物体的侵害是导致负密度制约效应发生的主要原因。区别不同类型的有害生物在负密度制约效应中的相对重要性是近年来研究的一个热点和难点问题。入侵木本植物从一个区域引入到新的区域后，天敌的逃逸是否影响了负密度制约效应的发生。我们以入侵植物为研究对象，在其原产地和入侵地，采用野外调查、野外同质园、室内控制试验的实验手段，研究入侵植物从原产地入侵到新的区域后，天敌逃逸是否决定了入侵植物逃离负密度制约效应的限制。我们发现土壤病原微生物决定了外来入侵植物原产地和入侵地的负密度制约效应。天敌逃逸导致入侵植物仅逃离了植食性昆虫所造成的负密度制约效应，而土壤病原微生物所造成的负密度制约效应依旧存在。揭示不同类别的天敌在负密度制约效应中的相对重要性，对于阐明木本植物的入侵机制以及开展合理有效的生物防治具有指导意义。