A Baseline Assessment of Invasive Alien Plant Species (IAPS) in Bhutan’s Jigme Singye Wangchuck National Park: Distribution Patterns, Invasion Hotspots and Management Implications

Invasive alien plant species (IAPS) are major drivers of biodiversity loss and ecosystem degradation, particularly in biodiversity-rich and topographically complex regions. This study presents the first systematic assessment of IAPS in Jigme Singye Wangchuck National Park (JSWNP), Bhutan, based on 375 vegetation plots surveyed along 16 transects using an adaptive sampling approach. We recorded 25 unique IAPS, including four listed among the world’s 100 worst invasive species. Ageratina adenophora was the most dominant and widespread species, present in over 60% of plots, followed by Solanum viarum , Bidens pilosa , and Chromolaena odorata . Species richness was highest in the southeastern and southwestern lowland zones, particularly within the Tingtibi and Nabji ranges. Chi-square tests revealed significant associations of many IAPS with altitude classes and habitat types, indicating that both environmental and anthropogenic factors influence their distribution. Spatial hotspot maps identified high-density invasion zones in disturbed and accessible areas. These findings provide a critical baseline for understanding IAPS spread in Himalayan protected landscapes and offer actionable insights for targeted management, early detection, and community-based intervention strategies to safeguard native biodiversity.