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并取代本地植被。入侵物种被认为是仅次于栖息地丧失对本地多样性的影响，但允许植物成为入侵的机制仍然知之甚少。摘要本研究拟对北美本土植物、欧洲外来入侵植物大一枝黄花（Solidago gigantea）的入侵机制进行研究。我们计划测试增强竞争能力的进化（EICA）假说，该假说认为，由于在引进范围内可能没有专门的天敌，外来植物可能会进化到在抗食草动物防御方面投入较少，从而获得比本地植物更大的竞争优势。在一系列的实验中，我们将比较欧洲和美国的黄花，包括它们的防御化学，它们在有和没有食草动物的情况下的表现，以及它们支持专一昆虫和通才昆虫生长的能力。EICA假说预测，欧洲黄花在次生化合物上的投资较少，因此应该支持更好的昆虫性能，并且在没有食草动物的情况下具有生长优势。最近的一些研究表明，如果对草食的耐受性或在草食损害后的恢复能力与适应性成本有关，那么与美国的黄菊花相比，欧洲黄菊花的补偿损害能力也会降低。

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.