Abstract. Introduction: There is a large information gap on the occurrence of non-native species and their impacts on native biodiversity in the Amazon region in Brazil. Objective: The objective of this study was to characterize the floristic composition of a protected area in Manaus, Amazonas, and assess the potential impact of non-native invasive species. Methods: A floristic survey was carried out in 30 plots measuring 20 x 20 m with 1 x 1 m subplots. The estimated parameters were density, frequency, dominance, Importance Value Index (IVI), and Environmental Impact of Non-Native Species (IIAE). Results: In total, 8 out of 264 species registered in the tree-shrub layer were not native. A total of 61 species were identified in the herbaceous layer, five of which were non-native. The impact is estimated based on the highest abundance of species of non-native species. Conclusions: The presence of non-native species in the study area is an indication of a potential impact on biodiversity and ecosystem functions.

Artocarpus heterophyllus is an invasive exotic species known for its negative impacts on Brazilian ecosystems. The aim of this study was to evaluate the distribution and population structure of A. heterophyllus in the plant community of a forest fragment in the Amazon. Individuals of this species were subject to active search at Sumaúma State Park, in Manaus, and two plots were delimited, where these individuals were counted. In each plot, the jackfruit tree individual with the largest Diameter at Breast Height (DBH) was centralized, and from it, native species were inventoried. The parameters of relative density, relative dominance and the importance value index were estimated. Jackfruit tree individuals in the plots had grouped distribution and their number in plots 1 and 2 was 308 and 872 individuals, respectively. In quadrant 1, 254 jackfruit trees and 118 native individuals were recorded, and in quadrant 2, 629 jackfruit and 130 native individuals. The jackfruit tree reached indices higher than the sum of the phytosociological indices of all native species.  Jackfruit tree distribution was considered similar to that occurring in other already invaded areas of Brazil, which may indicate that the same impacts may occur in Amazonian ecosystems.