Collaborative Research: Does Escape From Natural Enemies Contribute to Invasiveness of Introduced Plants? A Test of the Evolution of Increased Competitive Ability Hypothesis

外来入侵植物目前是对自然地区的主要威胁，因为它们可以在社区中传播，取代本地植被。据信，入侵物种对当地多样性的影响仅次于栖息地丧失，但允许植物成为入侵物种的机制仍然知之甚少。我们建议研究一枝黄花的侵袭机制，一枝黄花原产于北美，是欧洲的外来入侵物种。我们计划测试增强竞争能力进化(EICA)假说，该假说认为，由于引进的范围可能没有专门的天敌，外来植物可能进化为在抗草食动物防御方面投入较少，从而获得相对于本土植物的竞争优势。在一系列实验中，我们将比较欧洲和美国黄花的防御化学成分，它们在食草动物存在和不存在的情况下的表现，以及它们支持专业昆虫和多面手昆虫生长的能力。EICA假说预测，欧洲的黄花应该在次生化合物上投资较少，因此应该支持更好的昆虫表现，并在没有草食动物的情况下具有生长优势。如果像最近的一些研究所表明的那样，对食草动物的耐受性或在食草动物受损后恢复的能力与健康成本相关，那么与美国黄花相比，欧洲黄花的补偿能力也将下降。

Invasive, exotic plants are currently a major threat to natural areas because they can spread through communities and replace native vegetation. Invasive species are believed to be second only to habitat loss in terms of their impact on native diversity, but the mechanisms that allow plants to become invasive are still poorly understood. We propose to investigate the mechanisms promoting invasiveness in Solidago gigantea, a species native to North America and an invasive exotic in Europe. We plan to test the Evolution of Increased Competitive Ability (EICA) hypothesis, which holds that because specialized natural enemies may be absent from the introduced range, exotic plants may evolve to invest less in anti-herbivore defenses and thereby gain a competitive advantage over native plants. In a series of experiments, we will compare European and US goldenrods in terms of their defensive chemistry, their performance in the presence and absence of herbivores, and their ability to support growth of both a specialist and a generalist insect. The EICA hypothesis predicts that European goldenrods should invest less in secondary compounds, and therefore should support better insect performance and have a growth advantage in the absence of herbivores. If tolerance to herbivory, or the ability to recover following herbivore damage, has associated fitness costs as suggested by some recent studies, then European goldenrods would also be expected to have reduced abilities to compensate for damage, compared to US goldenrods.