Abstract:

Objective: This study aims to explore species attributes and spatial occupation advantages that facilitate alien plants successful invasion, evaluate their ecological impacts on native plant communities, and reveal their invasion mechanisms, providing theoretical support for scientific prevention and control of alien plants. Method: A total of 824 sampling plots (1 m × 1 m) were established across Guangdong Province. First, based on five attribute characteristics of the species level: family and genus classification, geographical origin, introduction time, introduction pathway, and functional traits, species richness was used as an indicator of invasion to comprehensively evaluate the invasiveness of alien plants. Second, a Bayesian phylogenetic generalized linear mixed effect model was applied to analyze the differences in coverage, basal diameter, plant height, and aboveground volume at the individual plant level between alien and native plants. Finally, we tested whether an increase in the community proportion of alien plants in any single metric (richness, coverage, aboveground volume, or abundance) significantly suppressed the community occupancy proportions of native plants across the remaining three metrics to quantify the ecological impact of alien plants on native plant communities. Result: 1) Alien plants originated from broad geographic regions, predominantly from the Americas, and belonged mostly to large families and genera (Asteraceae, Euphorbia, Ipomoea, and Solanum), suggesting potential environmental preadaptation. The introduction time of alien species was primarily concentrated between 1840 (the First Opium War) and 1949 (the founding of the People’s Republic of China), with introduction of ornamental plants being the dominant pathway, highlighting the crucial influence of human activities. In terms of growth forms, alien plants were dominated by herbaceous plants, plants of a single growth form, and perennial herbs, exhibiting “ideal weed” advantages such as rapid growth, targeted resource acquisition, and long-term establishment capacity. 2) Alien plants exhibited significantly higher coverage than native plants (P<0.001), however, there were no significant differences in basal diameter, plant height, or aboveground volume between alien and native plants, reflecting a lateral expansion strategy and coverage dominance in alien plants. 3) Alien plants exerted a systemic suppressive effect on native plant community structure. An increase in the community proportion of alien plants for any single metric (richness, coverage, aboveground volume, or abundance) significantly suppressed the community occupancy proportions of native plants across the remaining three metrics (P<0.001). Conclusion: This study elucidates the mechanisms driving the successful invasion and suppression of native plant communities by alien plants from multiple dimensions: human introduction acts as the primary driver of invasion, environmental preadaptation lays the foundation for cross-regional establishment, the generalist phenotypes of “ideal weeds” promote population persistence and spread, and coverage dominance via lateral expansion provides the pathway for the systemic suppression of native plant communities.

Key words: alien plants, invasiveness, preadaptation, anthropogenic influences, traits, Guangdong Province