Variation in the Composition and Biodiversity of Native Trees in Tropical Forests: Effects of Invasive Species, Topography, and Habitat

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ABSTRACT Aims Understanding the role of invasive species in ecological communities, and how native and invaders interact to shape the composition, biodiversity, and structure of contemporary forests, is crucial for effective management and conservation action. This is especially important in tropical regions, for which the mechanisms and consequences of invasion remain understudied compared to temperate forests despite increasing research on the effects of invasives during recent decades. Here, we evaluate the roles of invasive species composition, topography, and habitat in shaping the composition and biodiversity of native tree communities in tropical forests. Location Puerto Rico, United States. Methods We analysed data from 188 permanent plots across closed‐canopy and post‐agricultural secondary forests. Multivariate analysis of variance and variation partitioning were used to quantify the contributions of invasive species composition (NMDS axes derived from species‐level densities [stems/ha]), habitat (forest type, soil type, forest age, historical land use), and topography (elevation, slope, aspect) to variation in native tree composition and biodiversity. Analyses were conducted island‐wide and within each of three forest types (dry, moist, and wet forests). Results Invasive species composition, habitat, and topography explained ~14% of the variation in native tree composition and ~39% of the variation in biodiversity. Invasive species composition, forest type, forest age, elevation, and slope were the primary characteristics accounting for such variation at both scales (island‐wide and within each forest type). The full models for native composition and biodiversity were significant at both scales. The relative importance of invasive species composition, habitat, and topography on the composition and biodiversity of native tree communities differed among forest types, but general patterns were the same, with habitat characteristics explaining the greatest amount of variation, followed by topography and invasive species composition. Main Conclusions Invasive species modify the composition and biodiversity of native trees in Puerto Rico. Combined with land‐use changes and habitat attributes, they have the potential to significantly alter the composition of tropical forests, with long‐term consequences for biodiversity management and conservation.

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