We used meta-analyses to examine experimental evidence that functional similarity between invaders and resident communities reduces invasion. We synthesized evidence from studies that experimentally added seed to resident communities in which the functional group composition had been manipulated. We found communities containing functionally similar resident species reduced invasion of forb but not grass invaders. However, experimental design dramatically influenced the results – with evidence for limiting similarity only found in artificially assembled communities, and not when studies used functional group removal from more ‘natural communities’. We suggest that functional group similarity plays a limited role in biotic resistance in established communities.

我们用元分析（meta-analyses）检验了入侵者和本土群落之间的功能相似性能减少入侵的试验证据。我们综合了向人工操控功能群结构的本土群落中试验性的添加种子的研究。我们发现含有功能相似的本土物种的群落降低了非禾本草本植物的入侵但是不能降低禾草类入侵种的入侵。然而，实验设计显著影响了实验结果：相似功能群减少入侵仅在人工组建的群落中发现，不能在从更“自然的群落”中去除功能群的研究中发现。因此，我们提出相似功能群在已有群落的生物抵抗方面的作用很有限。

The principle of limiting similarity suggests that species must be functionally different to coexist; based on the assumption that inter-specific competition should be greatest between functionally similar species. There has been controversy over the generality of this assembly rule for plant communities with some studies finding evidence for limiting similarity and others not. One approach to testing this is to examine the ‘invasion’ success of species into communities in which the functional group composition has been manipulated. Using a meta-analysis approach, we examined the generality of limiting similarity for plant communities based on published experimental studies. We asked – is establishment of an invading species less successful if it belongs to a functional group that is already present in the community compared to a community in which that functional group is absent? We explored separately colonisation (i.e. germination, establishment or seedling survival) and performance (i.e. biomass, cover or growth) of different functional groups (forbs and grasses) and experimental designs (removal experiments of more or less natural communities and synthetic-assemblage experiments). We found that communities containing functionally similar resident species did reduce invader colonisation and performance of forb invaders, but did not reduce colonisation or performance of grass invaders. Evidence in support of limiting similarity was only detected in synthetic-assemblage experiments and not when studies used functional group removal from ‘natural’ communities. Functional similarity is an important aspect of biotic resistance for forb invaders, but was only found in artificial communities. This has implications for restoration ecology especially when communities are built de novo. However, we suggest that limiting similarity plays a limited role in biotic resistance, because no evidence was detected in established communities. 基于功能相似的物种之间的竞争应该最强的假设，限制相似性理论指出功能不同的物种方能共存。该群落理论的一般性仍存在争议因为限制相似性被有些研究证实也被其它一些研究否定。检验该理论的方法之一是看人工操控功能群结构的群落中物种入侵的成功与否。基于发表的试验研究，采用元分析（meta-analyses）的方法我们检验了限制相似性在植物群落中的一般性。我们的问题是：相比在一个其所属功能群缺失的群落中，某入侵物种是否在其所属功能群存在的群落中的入侵更不成功？我们分别研究了不同试验设计（在差不多自然的群落中进行移除试验或人工组建不同群落）条件下不同功能群（非禾草类草本和禾草类）的进入过程（即：种子萌发、生长或幼苗成活）和进入后的生长表现（即：生物量、盖度或生长速度）。我们发现含有功能相似的本土物种的群落确实减少了非禾草类草本入侵者的进入和生长表现，但是没有减少减弱禾草类入侵者的进入和生长表现。支持限制相似性的证据仅存在于人工组建群落的试验中而没有在采用从”自然“群落中移除功能群的试验中发现。功能相似性是抵抗非禾草类草本入侵者的一个重要方法但是仅对人工群落有效。该结果对于恢复生态学（尤其当群落是从新开始时）很有意义。尽管如此，我们指出在生物抵抗方面限制相似性的作了有限，因为在已有的群落（自然群落）中没有这方面的证据。