Elevation-Driven Shifts in Species Diversity, Endemicity, and Vegetation Structure across the Mount Hamiguitan Range Wildlife Sanctuary, a UNESCO World Heritage Site in Davao Oriental, Philippines

Abstract

Mount Hamiguitan Range Wildlife Sanctuary (MHRWS) in Davao Oriental, Philippines, is among the country’s most ecologically diverse and geologically unique mountain ecosystems. Rising to 1,620 m above sea level and covering 6,834 ha, it is part of the Eastern Mindanao Biodiversity Corridor. Declared a national park in 2003 and designated a UNESCO World Heritage Site in 2014, Mt. Hamiguitan supports numerous endemic and threatened species through collaborative stewardship by national agencies, local governments, and indigenous communities. This study analyzed vegetation profiles and land cover types along Mt. Hamiguitan’s elevational gradient to clarify biodiversity patterns and ecological zonation. Sixteen vegetation quadrats were systematically established at 100-m intervals from 140-1,620 m above sea level. Species composition, forest type, and mean diameter at breast height (DBH) were recorded and integrated with satellite-derived land cover data and GIS analysis to evaluate habitat distribution and human influence. Five major forest formations were identified: agroecosystem (75–420 m), dipterocarp forest (420–920 m), montane forest (920–1,160 m), mossy forest (1,160–1,350 m), and mossy-pygmy forest (1,160–1,620 m). Elevation strongly influenced shifts in species diversity, endemicity, and vegetation structure. Lower elevations were dominated by agriculturally influenced species such as Ficus indica and Chrysophyllum cainito, while higher zones supported stunted, endemic taxa including Leptospermum flavescens and Tristaniopsis micrantha, adapted to ultramafic soils and cooler, wind-exposed environments. The study underscores Mt. Hamiguitan’s role as a vertically stratified refuge for endemic biodiversity and highlights the need to protect high-altitude forests, restore buffer zones, and monitor climate-driven species shifts.