Karst ecosystems are critical refugia for various invertebrates including land snails. In the Philippines, data on these mollusks are insufficient amidst wide-scale habitat destruction due to uncurbed tourism and mineral extraction activities. To address this research gap, land snail diversity and community assemblage in the historic Biak-Na-Bato National Park (BNBNP), San Miguel, Bulacan were examined. A total of 32 5x5m quadrats were randomly set around the vicinity of four accessible caves: Santol, Bahay Paniki, Cuarto-Cuarto, and Aguinaldo, during dry and wet seasons. Environmental variables including altitude, temperature, relative humidity, soil moisture, soil pH, soil exchangeable calcium, number of trees, diameter of trees, canopy cover, and leaf litter depth were measured. From a total of 2,834 land snails sampled, 42 species and 14 families were identified. From these, 23 were classified as macro (> 5 mm) and 18 as micro (< 5 mm) land snails, and one as a slug. Moreover, 37 (88.10%) were native species while 5 (11.90%) were non-native. Bahay Paniki recorded the highest species richness but lowest diversity (27 species/qD = 5) whereas Aguinaldo exhibited the highest overall diversity (23 species/qD = 12). Relatively high sample coverage values (> 0.95) suggest increasing sampling effort to detect rare species. PERMANOVA and NMDS showed significant difference in community assemblage between sites. Cyclophorus appendiculatus attained the highest contribution (34.01%) to site dissimilarity. Land snail assemblages were influenced by temperature, soil pH, soil calcium, number of trees, tree diameter at breast height, and soil moisture based on CCA. The GLMM identified soil pH as the strongest predictor of species richness, while abundance was best explained by a combination of canopy cover, number of trees, soil moisture, soil pH, and temperature. This study reveals BNBNP's distinct malacofaunal diversity, underscoring its significance as a karst ecosystem that warrants continued conservation.
Biak-Na-Bato National Park, Malacofauna, Karst, Caves, Macro land snail, Micro land snail
