Assessment of Invasive Alien Plants in the Ecotourism Site of Mount Timolan Protected Landscape, Zamboanga del Sur, Philippines

Invasive alien plant species (IAPS) act as biological pollutants that drive biodiversity loss by altering the dynamics of native plant communities. This is particularly alarming when IAPS encroach on protected areas such as the Mount Timolan Protected Landscape (MTPL). This study, thus, investigated the prevalence of IAPS in an ecotourism site within MTPL, Zamboanga del Sur, Philippines. The modified belt-transect and nested quadrat sampling methods were employed, documenting 55 native and 11 introduced plant species, including 4 IAPS: Odontonema cuspidatum (Nees) Kuntze, Spathodea campanulata P. Beauv., Gmelina arborea Roxb. ex Sm., and Piper aduncum L. The Wilcoxon signed-rank test revealed that the area was generally dominated by native plants, as evidenced by the significantly lower median relative abundance of IAPS compared to native species. Notably, plots with the highest diversity (plot 2) and evenness (plot 3) indices were dominated by native species, whereas the plot with the lowest diversity and evenness (plot 5) was dominated by IAPS. The Spearman's rank correlation showed significant negative relationships between IAPS relative abundance and both species diversity and evenness, suggesting that higher IAPS prevalence is associated with lower species diversity and less balanced plant community structure. While IAPS were found to be relatively lower in abundance compared to native species in the site, their confirmed presence raises significant concern in the protected area, thereby highlighting the need for implementing proactive, evidence-based management strategies, including monitoring, containment, and targeted control measures to limit further spread. This study contributes to the achievement of Sustainable Development Goal Target 15.8 and the Kunming–Montreal Global Biodiversity Framework Target 6, which aim to avert the introduction of invasive alien species, control their spread, and reduce their impacts.