AgResearch Limited, 1365 Springs Road, Christchurch, 8140, New Zealand.
Bio-Protection Research Centre, Lincoln University, PO Box 84, Lincoln, 7647, New Zealand.
Ecol Lett. 2019 Jun;22(6):1038-1046. doi: 10.1111/ele.13261. Epub 2019 Mar 28.
The degree to which plant communities are vulnerable to invasion by alien species has often been assessed using the relationship between native and alien plant species richness (NAR). Variation in the direction and strength of the NAR tends to be negative for small plot sizes and study extents, but positive for large plots and extents. This invasion paradox has been attributed to different processes driving species richness at different spatial scales. However, the focus on plot size has drawn attention away from other factors influencing the NAR, in part because the influence of other factors may be obscured by or interact with plot size. Here, we test whether variation in the NAR can be explained by covariates linked to community susceptibility to invasion and whether these interact with plot size using a quantitative meta-analysis drawn from 87 field studies that examined 161 NARs. While plot size explained most variation, the NAR was less positive in grassland habitats and in the Australasian region. Other covariates did not show strong relationships with the NAR even after accounting for interactions with plot size. Instead, much of the unexplained variation is associated with article or author specific differences, suggesting the NAR depends strongly on how different authors choose their study system or study design.
植物群落对入侵物种的脆弱性程度通常通过本土和外来植物物种丰富度（NAR）之间的关系来评估。对于小面积和小研究范围，NAR 的方向和强度变化往往是负的，但对于大面积和大范围，NAR 的方向和强度变化往往是正的。这种入侵悖论归因于不同的过程在不同的空间尺度上驱动物种丰富度。然而，对斑块大小的关注使得人们忽略了其他影响 NAR 的因素，部分原因是其他因素的影响可能会被斑块大小掩盖或相互作用。在这里，我们使用来自 87 项野外研究的定量荟萃分析来检验 NAR 的变化是否可以用与群落易感性入侵相关的协变量来解释，以及这些协变量是否与斑块大小相互作用。虽然斑块大小解释了大部分的变化，但在草原生境和澳大拉西亚地区，NAR 的正性较小。即使考虑到与斑块大小的相互作用，其他协变量与 NAR 之间也没有很强的关系。相反，大部分未解释的变异与文章或作者特定的差异有关，这表明 NAR 强烈依赖于不同作者如何选择他们的研究系统或研究设计。
