Spatial distribution of three snail species, including the invader Potamopyrgus antipodarum , in a freshwater spring

The highly invasive New Zealand mudsnail, Potamopyrgus antipodarum , may compete with and displace native North American macroinvertebrates in freshwater systems wherever it becomes established. Densities and spatial distributions of 3 snail species including P. antipodarum and the threatened Taylorconcha serpenticola were compared among 3 adjacent habitat types (run, edge, and vegetation) in Banbury Springs, a tributary of the Snake River, near Hagerman, Idaho, USA. In all 3 habitats P. antipodarum was the most abundant snail species. All 3 species densities were highly variable within habitats, suggesting a nonrandom distribution pattern. Densities of P. antipodarum were significantly greatest in the vegetation habitat type, while densities of T. serpenticola were similar among habitats. Smallersized P. antipodarum were less abundant in the run habitat with its associated higher water velocities, and their densities were negatively correlated with velocity. Densities of P. antipodarum also were negatively correlated with distance from the highly infested, man-made Morgan Lake, while T. serpenticola densities were positively correlated with distance from Morgan Lake. Potamopyrgus antipodarum is a potential competitor with native aquatic species, although its colonization into some freshwater habitats may be limited.