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.