Does the Species Number of Invasive Plants Regulate the Intensity of Interspecific Interactions Among Multiple Plants Under Different Invasion Scenarios?

Multiple invasive plants (IPS) can coexist in the same community. The intensity of interspecific interactions among multiple plants may progressively alter with the differences in the species number of IPS (<i>S_i</i>) under different invasion scenarios. However, the correlation between plant taxonomic diversity, <i>S_i</i>, the invasion intensity of IPS, the community invasibility and the intensity of interspecific interactions among multiple plants under different invasion scenarios remains unclear. This study aims to estimate the differences in the intensity of interspecific interactions among multiple plants, the taxonomic diversity of plants, the invasion intensity of IPS and the invasibility of the plant community under different invasion scenarios along a gradient of <i>S_i</i>. This study used a comparative field survey method in four cities in Jiangsu (including Lianyungang, Yancheng, Nantong and Zhenjiang), China. The species number of plants and plant richness decreased under the mono-invasion achieved by one IP compared to the uninvaded communities. Plant taxonomic diversity was negatively associated with the invasion intensity of IPS and the community invasibility. Plant taxonomic diversity was positively associated with <i>S_i</i>. The intensity of interspecific interactions among multiple plants decreased across all invasion scenarios. The intensity of interspecific interactions among multiple plants showed a significant positive association with the ratio of the max and min relative coverage of all plants, but a significant negative association with plant evenness. Therefore, the ratio of the max and min relative coverage of all plants and plant evenness may be the main factor regulating the intensity of interspecific interactions among multiple plants under different invasion scenarios, rather than <i>S_i</i>.