Invasion hotspots in wilderness zones of tropical national parks

Invasive alien plant species increasingly threaten the integrity of forest ecosystems in protected areas, particularly within poorly studied wilderness zones of tropical national parks. The aim of this study was to assess the spatial distribution and invasion intensity of invasive alien plant species in the wilderness zone of Gunung Ciremai National Park, West Java, Indonesia. During the wet season, a comprehensive geographical investigation was conducted using twelve systematically established plots (20 × 20 m) with nested subplots representing different growth stages. A total of 18 invasive alien plant species belonging to nine families were recorded. Hierarchical cluster analysis identified three statistically distinct invasion intensity zones: a moderately invaded zone (67% of plots) dominated by Panicum maximum and Isachne globosa; a highly invaded zone (25% of plots) characterised by strong dominance of the woody legume Calliandra calothyrsus; and a low-invasion zone (8% of plots) with minimal establishment. Between-cluster Bray-Curtis dissimilarity (0.72 ± 0.18) exceeded within-cluster values (0.52-0.65), indicating pronounced compositional differentiation. A corridor-based invasion pattern was supported by a significant decline in invasion intensity with increasing distance from trails (R² = 0.78, p < 0.001). The study provided the first quantitative spatial assessment of invasive plant distribution in wilderness zones of Indonesian protected areas and demonstrated the value of multivariate analyses for identifying invasion hotspots and informing targeted management strategies