Are the anthropized Cerradão of the Cerrado-Pantanal ecotone resistant to alien species invasion?

Alien species pose a potential threat to biodiversity, necessitating vigilant monitoring to inform effective control strategies and prevent their invasiveness. The primary objective of this study was to evaluate the impact of alien species on the richness, horizontal structure, and diversity of the tree–shrub layer within a Cerrado-Pantanal transition region fragment. A floristic census was conducted across a fragment of approximately 3.0 ha, measuring all individuals with an aboveground diameter (DAG) ≥ 5.0 cm. The study assessed the statistical significance of diversity variation in the presence and absence of alien species using the Hutcheson t-test and examined the correlation between the proportion of alien species and various community parameters through Pearson’s correlation. The findings revealed a total of 84 species belonging to 34 families, with a total of 2218 recorded individuals. Notably, eight species (9.52%) were identified as alien, distributed across five families. Among the alien species, Leucaena leucocephala (Lam.) de Wit exhibited the highest importance value. However, the analysis indicated that the presence of alien species did not yield a significant variation in diversity, as demonstrated by the applied test with a 5.0% probability level, at both the plot and community levels. Moreover, the correlation analysis indicated that the community variables exhibited a low association with the proportion of individuals belonging to alien species. Specifically, the correlation decreased in the following order: Shannon–Weaver Diversity Index, density of native species, basal area of native species, and richness of native species. The observed low correlation coefficients (r) and nonsignificant p-values (p < 0.05) suggested that the presence of alien species did not exert a significant influence on the richness, structure, and diversity of the tree–shrub layer within the studied fragment. This outcome was likely facilitated by the absence of dominant populations of alien species. Thus, the study concludes that, at least within this specific context, alien species do not exert a significant influence on the assessed community parameters.