Abstract:
Sri Lanka is reported with highly diverse and endemic land snail fauna. Nevertheless, it is greatly
under sampled while data are scarce on their micro-habitat preferences, which are critical for
land snail conservation decision making due to their limited mobility and high susceptibility to
predation. Here we have investigated the micro-habitat factors that influence variation of species
richness and diversity of land snail fauna along an elevation gradient from 100 m to 2,200 m, in
order to see whether those malacofaunal communities differ significantly with the elevation
dependent features of their micro-habitat. The investigation was conducted along a transect from
Udawalawe to Horton Plains National Parks in the upper catchment of the Walawe basin in Sri
Lanka, by collecting specimens through time restricted searches within twelve 10×10 m
quadrats, from November 2017 to February 2018. Nine micro-habitat variables viz. soil moisture,
soil pH, litter depth, soil temperature, air temperature, canopy cover, undergrowth cover, deadwood
content and tree density were measured for each quadrat. Correlation analysis followed by
regression was used to establish the relationships between the micro-habitat variables and land
snail species richness, diversity, percentage endemism and threatened percentage. The present
study populated a database of 770 records of live land snails and shells of dead specimens,
representing 33 species belonging to nine families, with 80% of species endemic to Sri Lanka,
including a possibly undescribed Cyclophorid. Family Ariophantidae (13 species; 55.7%)
represented the highest number of specimens including the most abundant species (Euplecta
acuducta; 16.8%), followed by Glassulidae (5 species). The results of the present study reveals
that micro-habitat variables directed by the elevation have influenced the land snail richness and
diversity variation along the transect. Increasing litter depth (r=0.71; p=0.01) and tree density
(r=0.771; p=0.003) were recorded to highly influence the species richness, while the land snail
diversity (Simpson Index) had a strong relationship with the soil moisture content (r=0.719;
p=0.003). Percentage species endemism of land snails was highly correlated with the soil
moisture (r=0.798; p=0.002) and the soil temperature (r=0.786; p=0.002). Canonical
Correspondence Analysis identified soil temperature, litter depth and soil moisture as the major
micro-habitat variables associated with land snail distribution while indicator species have been
identified for each micro-habitat variable.
