Invasive alien plants are often found to be more plastic than the natives, which enable the former to outperform the native plants under some, or in a wide range, of environmental conditions. In addition, their performance under non-competitive conditions might not predict their performance under competitive conditions. The performance of the recent invader, Eupatorium catarium, was compared with that of a historical invader, Ageratum conyzoides, and a common native plant, Vernonia cinerea, under varying levels of light and moisture with and without competition. When grown alone and in response to decreases in light levels, E. catarium and V. cinerea were more plastic in their root-to-shoot ratio than A. conyzoides, while V. cinerea was more plastic in its specific leaf area (SLA) than E. catarium and A. conyzoides. Eupatorium catarium was more plastic than A. conyzoides and V. cinerea in the SLA in response to the drought treatment. However, these differences in trait plasticities did not lead to a difference in biomass production under each light and moisture treatment combination. When E. catarium was competing with either A. conyzoides or V. cinerea, the interacting species also did not differ in their biomass production and relative interaction intensity under each light and moisture treatment combination. These results indicate that the two invasive species and the native plant do not differ in their performance under relatively low soil nutrient conditions, regardless of the moisture, light and competition treatments that are imposed. Therefore, E. catarium and A. conyzoides cannot outperform V. cinerea under low nutrient conditions, regardless of the light and water availability.

中文翻译：

---

与普通本地植物在不同光照和湿度水平下相比，侵入性紫茎泽兰和 Ageratum conyzoides 的性能

人们经常发现外来入侵植物比本地植物更具可塑性，这使得前者在某些或广泛的环境条件下表现优于本地植物。此外，他们在非竞争条件下的表现可能无法预测他们在竞争条件下的表现。将最近的入侵者 Eupatorium catarium 的性能与历史入侵者 Ageratum conyzoides 和一种常见的本地植物斑鸠菊属植物的性能进行了比较，它们在不同程度的光照和湿度条件下有竞争和无竞争。当单独生长并响应光照水平降低时，E. catarium 和 V. cinerea 的根茎比比 A. conyzoides 更具可塑性，而 V. cinerea 在其比叶面积 (SLA) 中更具塑性比 E. catarium 和 A. conyzoides。Eupatorium catarium 在 SLA 中比 A. conyzoides 和 V. cinerea 更具可塑性，以响应干旱处理。然而，这些性状可塑性的差异并未导致每种光照和水分处理组合下生物质产量的差异。当 E. catarium 与 A​​. conyzoides 或 V. cinerea 竞争时，相互作用的物种在每种光和水分处理组合下的生物量产生和相对相互作用强度也没有差异。这些结果表明，无论施加何种水分、光照和竞争处理，这两种入侵物种和本地植物在相对低的土壤养分条件下的性能没有差异。因此，E. catarium 和 A. conyzoides 在低营养条件下不能胜过 V. cinerea，