Urbanization Impacts on Land Snail Community Composition

Urbanization has tremendous impacts on most native species. Urban ecosystems are becoming increasingly prevalent, while urban ecology is a relatively underdeveloped field. This is especially true for terrestrial mollusks, which are a surprisingly understudied organism. Due to their low mobility and dispersal potential, land snails are valuable indicators of ecosystem disturbance. For this study, land snails were collected in 54 city parks along an urban gradient to understand influences of urbanization on snail communities. Sampled parks include small extensively landscaped downtown parks, neighborhood and community parks, district parks, and large nature parks, each with variable vegetation, soil characteristics, disturbance regimes, and human activities. Sampling recovered 12,153 individual snails, representing 20 families, 43 genera, and 95 species. Seven new Tennessee state and 87 new county occurrences were recorded for Davidson, Knox, Hamilton, and Marion counties. Five non-native and one extra-limital invasive species were found, four of which are new Tennessee state records. Results show that urbanization greatly alters land snail community structure. Nature and district parks have significantly greater species richness, species diversity and species evenness than community, neighborhood, and downtown parks. Degradation of parks, distance from the park to the city center and percent of coarse woody debris explained most of the variation between park types. Non-metric multidimensional scaling shows that downtown snail communities are similar across all three cities, whereas snail communities in nature parks are distinct. This suggests that urbanization promotes homogenization among land snail communities in Tennessee.