Climate-induced habitat contraction and elevational redistribution of Selaginella willdenowii and S. intermedia in Southeast Asia

Abstract. Setyawan AD, Sutarno, Sugiyarto, Sunarto, Nursamsi I, Budiharta S, Supriatna J, Pradhan P. 2025. Climate-induced habitat contraction and elevational redistribution of Selaginella willdenowii and S. intermedia in Southeast Asia. Asian J For 9: 440-455. Climate change is increasingly recognized as a major threat to tropical biodiversity, particularly for moisture-dependent cryptogams with narrow environmental requirements. This study assessed the current and future habitat suitability of Selaginella willdenowii and Selaginella intermedia across Southeast Asia using Maximum Entropy (MaxEnt) modeling. A total of 726 occurrence records for S. willdenowii and 679 records for S. intermedia were compiled from field surveys conducted across Java Island, Indonesia and verified records obtained from the Global Biodiversity Information Facility (GBIF). Models were developed using climatic, edaphic, topographic, and UV-B radiation variables and projected under four Representative Concentration Pathway (RCP) scenarios (RCP 2.6, 4.5, 6.0, and 8.5) for 2030, 2050, and 2080. The models showed high predictive performance, with AUC values exceeding 0.93 and TSS values exceeding 0.87. Annual precipitation, temperature, elevation, and UV-B radiation were identified as the most influential predictors of habitat suitability. Current suitable habitats were concentrated in mainland and maritime Southeast Asia, particularly in Indonesia, Peninsular Malaysia, and the Philippines. Java Island emerged as a major regional hotspot, supporting 57.7% and 48.9% suitable habitat coverage for S. willdenowii and S. intermedia, respectively. Future projections consistently indicated habitat contraction under all climate scenarios, with greater losses occurring under higher emission pathways and later projection periods. By 2080, suitable habitat was projected to decline by 16.9-23.4% for S. willdenowii and 27.3-33.2% for S. intermedia accompanied by pronounced upslope redistribution toward montane environments. The greater habitat loss predicted for S. intermedia reflects its stronger dependence on elevational gradients and narrower climatic niche. These findings identify montane landscapes as critical climate refugia and emphasize the importance of maintaining elevational connectivity to support the long-term persistence of tropical understory cryptogams under climate change.