Aridity and grazing are associated with reduced trait complementarity and higher invasion intensity of Solanum rostratum in native plant communities

1The biotic resistance hypothesis (BRH) of Elton posits that diverse communities are more resistant to biological invasions. While the effects of climatic stresses and human disturbances on community invasibility have been extensively studied individually, their combined and potentially interactive influences remain poorly understood.

To address this problem, a national-scale survey was conducted on 3000 km in China to assess the relationship between the intensity of Solanum rostratum invasion and the diversity of native species.

Our study found that sites with higher native plant biodiversity generally exhibited lower S. rostratum invasion intensity. Specifically, native plant diversity helped resist invasion by improving community complementarity, increasing community density, coverage, and biomass, promoting community weighted means (CWM) of resource-conservative traits, and reducing trait differences between invasive and native plants. Furthermore, biodiversity loss was associated with higher S. rostratum invasion intensity. Specifically, sites with higher aridity and grazing tended to have lower biodiversity, reduced community complementarity, decreased density, coverage, and biomass, and lower community-weighted means of resource-conservative traits. In particular, phylogenetic diversity (Faith’s PD)  and the Simpson index were more effective than species richness in predicting the resistance of local communities to invasion by S. rostratum and showed stronger negative correlations with invasion intensity.

Our results further supported the BRH and emphasized the importance of considering species richness, evenness, phylogenetic structure, and trait structure when explaining biological resistance to invasion. Overall, this study highlighted the crucial role of the diversity and structure of the native plant community in resisting S. rostratum invasion. Sites experiencing higher aridity and grazing were associated with reduced resistance to invasion, as indicated by lower biodiversity and reduced community complementarity*.* Therefore, conserving and restoring native plant diversity, particularly enhancing phylogenetic diversity and resource-conservative traits, can improve the resistance of the ecosystem to invasive species.