DIVERSITY AND ABUNDANCE OF LAND SNAILS (GASTROPODA: PULMONATA) IN LA MESA WATERSHED AND NATURE RESERVE

La Mesa Watershed and Nature Reserve is the major source of water in Metro Manila covering 2,000 hectares of total forest cover. Terrestrial snails are bioindicators of forest ecosystem conditions and play a vital role in ecosystem nutrient cycling. Assessment of land snail diversity were done during the periods of December 2016 and January 2017. Six 10m x 10m quadrats within the three regions (upper, middle and lower) of the forest cover were surveyed using time search method. Abundance and diversity of land snails were computed using Paleontological Statistics (PAST) ver 1.34 software. Physicochemical parameters were also correlated with snail diversity using Principal Component Analysis (PCA). A total of 235 land snails were collected belonging to 6 families and 10 identified species. Bradybaenidae family consists of three species ( Calocochlia bruguieriana, Cochlostyla sp., and Helicostyla daphnis) The families Helicarionidae and Achatinidae consist of two known species ( Epiglypta howeinsulae, and Nipponochlamys semisericata) , and ( Achatina fulica and Achatina wegensi ) respectively. The microsnails Vitrina fasciata and Cristigibba polingi belongs to the family Vitrinidae and Camaenidae respectively, and Ryssota lamarckiana is the sole species under family Chronidae. Epiglypta howeinsulae has the highest relative abundance with a mean of 36.30, while the rest have lower than 25.11. All sampling sites were characterized by having mean relative humidity of 75%, air temperature of 25.5 0 C, soil temperature of 23 0 C, soil pH of 6.24, soil moisture of 13.7 % and soil Calcium of 2956.67 mg/kg. High diversity of land snail in three sampling sites were correlated with soil pH, soil Calcium and relative humidity. La Mesa Watershed and Nature Reserve depicts a diverse land snail fauna having a Shannon diversity index (H’) of 1.744. The findings of this research may support the conservation efforts of endemic land snails and other wildlife found in the watershed.