Functional traits of both specific alien species and receptive community but not community diversity determined the invasion success under biotic and abiotic conditions

Abstract Biodiversity can provide some resistance to alien species in some cases, but not in others. The observed paradoxical results may be related to several reasons, including variations in abiotic and/or biotic conditions, alien species characteristics and the fact that the species number cannot adequately reflect native community diversity. A comprehensive study that incorporates these elements is lacking. We constructed invasion systems using nine alien plant species and 12 native communities, composed of two diversity levels (three vs. six species), under different nitrogen (N) and arbuscular mycorrhiza fungi (AMF) inoculation conditions. We used this fully crossed factorial experiment, that is, N (low vs. high) × native community diversity (three vs. six species) × AMF (with vs. without), to systematically explore the invasion success in native communities. We found that the species number of native community did not affect invasion success under any of the N or AMF conditions. The effects of N enrichment and AMF inoculation on invasion were not consistent between alien species and native communities based on their phenotypic plasticity of functional traits in response to N enrichment and AMF inoculation. Specifically, the changing of invasion in response to N enrichment and AMF inoculation was associated with the plasticity of plant height and root mass fraction that reflects the competitiveness for the acquisition of light and soil resources. Our results that species number did not capture well the resistance of the native community suggested that the simple expression of species richness is not realistic to describe the invasion resistance of the community. Additionally, the association between functional traits of both alien species and native communities and invasion success suggested that changes in competitive advantage and resource acquisition strategy are more important in explaining changes in invasive success in different N and AMF conditions. Future studies are needed to explore invasion success by systematically considering the characteristics of invasive species and the native community, and the specific abiotic and biotic conditions. Using functional traits may help advance our understanding of plant invasion in broad circumstances and shed light on a generalized framework of biological invasion. Read the free Plain Language Summary for this article on the Journal blog.