The impact of a biological invasion on native communities is expected to be uneven across invaded landscapes due to differences in local abiotic conditions, invader abundance, and traits and composition of the native community. One way to improve predictive ability about the impact of an invasive species given variable conditions is to exploit known mechanisms driving invasive species' success. Invasive plants frequently exhibit allelopathic traits, which can be directly toxic to plants or indirectly impact them via disruption of root symbionts, including mycorrhizal fungi. The indirect mechanism – mutualism disruption – is predicted to impact plants that rely on mycorrhizas but not affect non-mycorrhizal plant species. To assess whether invader-driven mutualism disruption explains observed changes in native plant communities, we analyzed long-term (1998–2018) plant cover data from forest plots across the state of Illinois. We evaluated native plant communities experiencing a range of abundance of invasive allelopathic garlic mustard Alliaria petiolata and varying environmental conditions. Consistent with the mutualism disruption hypothesis, we showed that as garlic mustard abundance increased over time in 0.25 m² sampling quadrats, the abundance of mycorrhizal plant species decreased, but non-mycorrhizal plant species did not. Over space and time, garlic mustard abundance predicted plant abundances and diversity at the quadrat level, but this relationship was not present at a larger scale when quadrats were aggregated within sites. Garlic mustard's impact on the plant community was highly localized, yet it was as important as abiotic variables for predicting local plant diversity. We showed that garlic mustard abundance was a key predictor of patterns of plant diversity across invasion intensity and environmental heterogeneity in a way that is consistent with mutualism disruption. Our work indicates that the mutualism disruption hypothesis can provide generalizable predictions of the impacts of allelopathic invasive plants that are evident at a broad spatial scale.

中文翻译：

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在不同的环境条件和不同的入侵强度中，入侵介导的互利共生破坏是显而易见的

由于当地非生物条件、入侵者丰度以及本地群落的特征和组成的差异，生物入侵对本地群落的影响预计在不同的入侵景观中是不平衡的。在给定可变条件的情况下，提高对入侵物种影响的预测能力的一种方法是利用已知的驱动入侵物种成功的机制。入侵植物经常表现出化感作用特征，这些特征可以直接对植物产生毒性，或者通过破坏包括菌根真菌在内的根共生体来间接影响植物。间接机制——互利共生破坏——预计会影响依赖菌根的植物，但不会影响非菌根植物物种。为了评估入侵者驱动的互利共生破坏是否解释了观察到的本地植物群落的变化，我们分析了伊利诺伊州森林地块的长期（1998-2018）植物覆盖数据。我们评估了经历了一系列丰富的入侵性化感蒜芥的本土植物群落Alliaria petiolata和不同的环境条件。与互利共生破坏假说一致，我们表明，随着时间的推移，大蒜芥末丰度在 0.25 m ^2中增加在采样样方中，菌根植物物种的丰度下降，但非菌根植物物种的丰度没有下降。在空间和时间上，大蒜芥菜丰度预测了样方水平上的植物丰度和多样性，但当样方在地点内聚集时，这种关系在更大范围内并不存在。蒜芥对植物群落的影响是高度局部化的，但它与预测当地植物多样性的非生物变量一样重要。我们表明，蒜芥丰度是入侵强度和环境异质性下植物多样性模式的关键预测因素，其方式与互利共生破坏一致。