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Abstract：
The evolution of increased competitive ability (EICA) hypothesis states that, when introduced in a novel habitat, invasive species may reallocate resources from costly quantitative defense mechanisms against enemies to dispersal and reproduction; meanwhile, the refinement of EICA suggests that concentrations of toxins used for qualitative defense against generalist herbivores may increase. Previous studies considered that only few genotypes were introduced to the new range, whereas most studies to test the EICA (or the refinement of EICA) hypotheses did not consider founder effects.In this study, genetic and phenotypic data of Chromolaena odorata populations sampled across native and introduced ranges were combined to investigate the role of postintroduction evolution in the successful invasion of C. odorata.Compared with native populations, the introduced populations exhibited lower levels of genetic diversity. Moreover, different founder effects events were interpreted as the main cause of the genetic structure observed in introduced ranges. Three Florida, two Trinidad, and two Puerto Rico populations may have been the sources of the invasive C. odorata in Asia.When in free of competition conditions, C. odorata plants from introduced ranges perform better than those from native ranges at high nutrient supply but not at low nutrient level. The differences in performance due to competition were significantly greater for C. odorata plants from the native range than those from the introduced range at both nutrient levels. Moreover, the differences in performance by competition were significantly greater for putative source populations than for invasive populations.Quantities of three types of secondary compounds in leaves of invasive C. odorata populations were significantly higher than those in putative source populations. These results provide more accurate evidence that the competitive ability of the introduced C. odorata is increased with postintroduction evolution.
摘要：
竞争能力增强(EICA)假说的演变指出，当被引入一个新颖的栖息地时，入侵物种可能会将资源从昂贵的定量防御机制重新分配给敌人的扩散和繁殖；同时，EICA的改进表明，用于对普通食草动物进行定性防御的毒素浓度可能会增加。以前的研究认为，只有很少的基因型被引入到新的范围，而大多数测试EICA(或EICA的细化)假设的研究没有考虑创始人效应.在这项研究中,将在本地和引入范围内采样的赤霉藻种群的遗传和表型数据相结合，以研究引入后进化在成功入侵赤霉的过程中的作用。与本地人口相比，引进种群的遗传多样性水平较低。此外，不同的创始人效应事件被解释为在引入范围内观察到的遗传结构的主要原因。三个佛罗里达，两个特立尼达,两个波多黎各人口可能是亚洲入侵的C.odorata的来源。当在没有竞争的条件下，在高营养供应但在低营养水平下，来自引入范围的C.odorata植物的表现要好于天然范围的植物。在两种营养水平下，来自天然范围的C.odorata植物由于竞争而产生的性能差异明显大于来自引入范围的C.odorata植物。此外，假定来源人群的竞争表现差异明显大于入侵人群。入侵C.odorata种群叶片中三种类型的次要化合物的含量显着高于假定的来源种群。这些结果提供了更准确的证据，表明引入的C.odorata的竞争能力随着引入后的进化而增加。
