Spatiotemporal modeling of the potential range distributions of Usnea in the Philippines under changing climate scenarios

This study presents the first ecological niche model for the lichen genus Usnea in the Philippines, utilizing MaxEnt to project both current and future habitat suitability under two Coupled Model Intercomparison Project Phase 6 climate scenarios (Shared Socioeconomic Pathways: 1-2.6 and 3-7.0) using EC-Earth3-Veg and MIROC6 models. Spatially filtered occurrence records and selected bioclimatic variables were used to build and optimize the model through the ENMeval R package. Results revealed that while Usnea currently occupies limited high-suitability areas, projections indicate a slight expansion in suitable habitats, especially in upland regions, driven by probable thermal niche shifts. Mean diurnal range (BIO2) is the dominant predictor under present conditions, whereas mean temperature of the warmest quarter (BIO10) controls future scenarios. Despite this, regional declines were observed in Western Visayas, Zamboanga Peninsula, Northern Mindanao, SoCCSKSarGen, and Bangsamoro Autonomous Region in Muslim Mindanao, which are areas characterized by warming and seasonal drying. These findings highlight both the potential resilience and vulnerability of Usnea, offering critical insights for conservation strategies in tropical montane ecosystems.