How an invasive tree reshapes the forest floor and alters amphibian occupancy through direct and indirect effects

Abstract Biological invasions can alter forest ecosystems, reshaping microhabitats and disrupting the interactions that sustain native communities. Among these invaders, the jackfruit ( Artocarpus heterophyllus ) has spread widely across the Atlantic Forest, where its ecological impacts remain poorly understood. We investigated how jackfruit density influences forest-floor structure and the occupancy of three leaf-litter amphibian species. Using generalized linear mixed models, occupancy modelling, and structural equation models (SEM), we evaluated both direct and indirect pathways linking invasion intensity to key habitat attributes, including leaf-litter depth, arthropod density and diversity, and amphibian occurrence. Jackfruit density had strong negative effects on litter depth and arthropod density, indicating habitat simplification and resource loss. Occupancy models revealed contrasting responses among species, with generalists more tolerant to invaded conditions and forest specialists negatively affected by invasion intensity or dependent on litter-mediated pathways. The SEM confirmed that invasion effects propagate through structural and trophic mechanisms, altering microhabitat structure and prey availability. Our results demonstrate that invasive trees can restructure forest-floor ecosystems through cascading physical and biological changes. These invasion-driven filters promote biotic homogenization by favoring disturbance-tolerant species while disadvantaging microhabitat specialists. Recognizing and mitigating these indirect pathways is critical for conserving amphibian diversity and maintaining the ecological resilience of tropical forests under increasing invasion pressure.