<p>Non-native tree species are restructuring tropical forest communities worldwide, yet the ecological dimensions and drivers of these transformations remain poorly understood. Using nearly two decades of standardized forest inventory data from Puerto Rico, we assessed how non-native tree species affect the biodiversity and composition in dry, moist, and wet forests. We examined diversity metrics, species abundance distributions, and community structure in relation to invasion intensity, quantified by both non-native species richness and abundance. Overall, non-native abundance, rather than non-native species richness, emerged as the most consistent predictor of ecological change. Across all forest types, increasing non-native abundance led to significant declines in native species abundance, richness, evenness, and diversity. These impacts were strongest in dry forest, where native richness declined by &gt; 90% under intense invasion. In moist and wet forests, effects were less severe, but reduced diversity and simplified community structure still occurred. Invasion intensity also altered native species composition at multiple scales. At the plot level, higher invasion intensity increased both compositional distinctiveness and dissimilarity. In contrast, β-diversity declined across invasion tiers, indicating large-scale biotic homogenization. These scale-dependent patterns reflect that invasions can drive structural divergence among plots and simultaneously reduce landscape-level heterogeneity through the loss of rare or specialized species. Our results highlight the profound, context-dependent effects of non-native species on tropical forest biodiversity. By integrating long-term data across forest types, we show that invasions reduce native diversity and contribute to biotic homogenization, emphasizing the need to incorporate invasion dynamics into forest management, conservation, and climate-change planning.</p>