Taxonomic and ecological assessment of invasive plant diversity along an altitudinal gradient on Mount Gamalama, Ternate Island, Indonesia

This study provides the first comprehensive assessment of invasive flora along the Mount Gamalama hiking trail, Ternate Island, Indonesia, a volcanically active ecosystem of high conservation value. Through exploratory surveys and taxonomic verification, this study documented 31 invasive species from 16 families and 29 genera across an elevational gradient of 369–940 m. Asteraceae was the dominant family (32.3 %), reflecting its global role in invasion dynamics. Most species originated from the Americas (41.9 %), introduced mainly through horticultural and agricultural pathways. The community structure was predominantly herbaceous (74 %), with shrubs (13 %) and lianas (13 %), consistent with global invasion trends. Nineteen species exhibited reported allelopathic activity, suggesting that chemical interference drives colonisation and competitive dominance. Taxonomic ratio analysis (Family/species (F/S) = 0.516; genus/species (G/S) = 0.935) indicated a balanced yet evolutionarily diverse assemblage, with no species of conservation concern under IUCN criteria. The results indicate that invasive plants are widely distributed across the surveyed altitudinal gradient and several species have documented allelopathic properties in previous studies. Together, these findings provide essential baseline data for monitoring and managing invasive species while supporting conservation planning in volcanic island ecosystems under increasing anthropogenic pressure.