生物入侵已经成为一个普遍性的环境问题，并为许多学者所关注。尽管一些理论研究和观察表明生物多样性丰富的群落不容易受到外来种的入侵，但后来有些实验研究并没能证实两者的负相关性，多样性可入侵性假说仍然是入侵生态学领域争论比较多的一个焦点。人为构建不同物种多样性和物种功能群多样性（C3 禾本科植物、C4植物、非禾本科草本植物和豆科植物）梯度的小尺度群落，把其它影响可入侵性的外在因子和多样性效应隔离开来，研究入侵种喜旱莲子草(Alternanthera philoxeroides)在不同群落里的入侵过程来验证多样性可入侵性及其相关假说。研究结果显示，物种功能群丰富的群落可入侵程度较低，功能群数目相同而物种多样性不同的群落可入侵性没有显著性差异，功能群特征不同的群落也表现出可入侵性的差异，生活史周期短的单一物种群落和有着生物固氮功能的豆科植物群落可入侵程度较高，与喜旱莲子草属于同一功能群且有着相似生态位的土著种莲子草(A. sessilis)对入侵的抵抗力最强。实验结果表明，物种多样性和群落可入侵性并没有很显著的负相关，而是与物种特性基础上的物种功能群多样性呈负相关，群落中留给入侵种生态位的机会很可能是决定群落可入侵性的一个关键因子。
Biological invasions are a pervasive environmental problem and are an important focus of ecological research and environmental management. Research on the function of biodiversity has stimulated an interest in the mechanisms underlying the invasibility of plant communities. Although many theoretical and observational studies suggest that diverse communities are more resistant to invasion by exotic species than less diverse communities, results of experimental studies are not conclusive and this remains a highly debated topic.
In this experiment, a series of manipulated grassland communities with different levels of species diversity and different species functional groups (16 species belong to C3 grasses, C4 plants, forbs and legume respectively) were established to test Elton‘s diversity-invasibility hypothesis by studying the pattern and process of invasion by Alternanthera philoxeroides. Total biomass of the invasive species, an index of community invasibility, was recorded in each community type. Our results showed that in communities with higher functional group diversity, the biomass of A. philoxeroides was significantly lower due to decreased niche opportunity whereas species diversity alone did not show any significant effects on the biomass of the invasive species. The results showed that community invasibility was negatively correlated with functional group diversity suggesting that the diversity of characteristics of species rather than species diversity itself was important. Niche opportunity for invasive species in communities might be a key determinant influencing its invasibility. The characteristics of functional groups also influenced the success of the invasion. Annual grasses with short life spans and nitrogen-fixing legumes were more susceptible to invasion. Moreover, A． sessilis, which belongs to the same morphological and functional group as A． philoxeroides, caused a significant decrease in establishment of the invader species. This suggests that competition might be more intense within functional groups than across functional groups. Because community invasibility is influenced by many factors and their interactions, the pattern and mechanisms of community invasibility are likely to be more complicated than we have acknowledged so far. More experimental work coupled with theoretical modeling studies are needed to better understand the characteristics of community invasibility.