Do Genetic Differences in Growth and Defense Contribute to the Success of an Invasive Plant Species? Experimental Tests

中国牛脂树（Sapium sebiferum）是墨西哥湾沿岸的主要入侵者，其侵略性地取代本地植物并形成单一的林分。在德克萨斯州和夏威夷进行的实验表明，入侵生态型的Sapium比亚洲（本地）生态型具有更高的生长速度，但防御能力较低，并且在夏威夷受到引进的亚洲食草动物的伤害更大。我们建议通过一系列的实验来回答以下问题：(1)高生长、低防御、低食草动物攻击的组合对Sapium的入侵成功有多重要？(2)在不同条件下，其生长和防御的差异对决定Sapium入侵的严重程度有多重要？(3)在北美入侵的Sapium生态型在类似的条件下在亚洲也能成功生长吗？这些实验将在Sapium状态和昆虫食草动物组合不同的野外站点重复进行。在德克萨斯州，Sapium是侵入性的，经历了低食草动物的压力，没有记录在案的专家；在夏威夷，Sapium是一种“偶然的外星人”，经历了非常高的通才食草动物压力，没有记录在案的专家；在中国，它的原产地是智属动物，它经历了来自智属动物专家的高食草压力。本实验将通过资源调控、植食性昆虫抑制和密度调控以及模拟植食性落叶等方法，研究本土和入侵生态型皂荚的生产性能和竞争能力。这些实验代表了对入侵植物和食草动物相互作用的独特研究，将阐明外来物种成功入侵本地群落的机制。这项研究的广泛影响是双重的。它将促进与中国科学家的合作，并培养中美研究生。它还将为未来入侵物种的预测提供实用信息，并有助于指导当前问题物种的管理。

Chinese Tallow Tree (Sapium sebiferum) is a major invader in the Gulf Coast thataggressively displaces native plants and forms monospecific stands. Experiments in Texas and Hawaii have shown that invasive ecotypes of Sapium have higher growth rates but lower defense abilities than Asian (native) ecotypes, and suffer higher damage from introduced Asian herbivores in Hawaii. We propose to use a series of experiments to answer the following questions: (1) How important is the combination of high growth, low defense and low herbivore attack for Sapium's invasion success? (2) How important are differences in its growth and defense in determining the severity of Sapium invasion in different conditions? (3) Are the same Sapium ecotypes that are invasive in North America also successful when grown in Asia in similar conditions? These experiments will be replicated across field sites that differ in Sapium status and insect herbivore assemblages. In Texas, Sapium is invasive and experiences low herbivore pressure with no documented specialists; in Hawaii, Sapium is a 'casual alien' that experiences very high generalist herbivore pressure with no documented specialists; and in China, where Sapium is native, it experiences high herbivore pressure from Sapium specialists. Our experiments will investigate the performance and competitive ability of native and invasive ecotypes of Sapium with resource manipulations, insect herbivore suppressions and density manipulations and simulated herbivore defoliation. These experiments represent a unique investigation into the interactions of invasive plants and herbivores that will elucidate the mechanisms by which exotic species successfully invade native communities. The broader impacts of the study are twofold. It will promote collaboration with Chinese scientists and train both Chinese and U.S. graduate students. It also will provide practical information for the prediction of future invasive species and help guide the management of current problem species.