Taxonomic and Functional Filters in Oil Palm Landscapes: How This Monoculture Reshapes Non-Volant Small Mammal Assemblages in the Amazon

Our objective was to evaluate the effects of converting Amazonian forest into oil palm plantations on the taxonomic and functional diversity of non-flying small mammal assemblages, and to identify the habitat and landscape variables shaping patterns of richness, composition, and abundance. Using pitfall and live traps in native forest and oil palm plantation areas, we recorded 201 individuals across 25 species. Richness and functional diversity indices did not differ between habitats; however, abundance was higher and evenness lower in oil palm plantations. Species composition differed between habitats, driven by species turnover, indicating that assemblages in oil palm plantations constitute a distinct set of species rather than a subset of the forest community. Canopy openness and understory density were the environmental determinants of abundance and composition, respectively. Our results show that oil palm monoculture reshapes small mammal communities through compositional turnover and shifts in dominance, favoring disturbance-tolerant generalists over forest specialists, without causing significant losses in richness or functional diversity, a pattern consistent with functional redundancy. Conserving and ecologically connecting the “Legal Reserve” forest fragments distributed across this landscape is essential to sustain disturbance-sensitive, forest-structure-dependent species that do not find suitable conditions within oil palm plantations.