The world-wide invader, the New Zealand mud snail (Potamopyrgus antipodarum) has established populations in the American west and in the Great Lakes region of North America. In the summer of 2013, the species was found in a high quality trout stream, Spring Creek, in Centre County, Pennsylvania. The goals of this study were to 1) determine the geographic distribution of the invader in central PA, 2) determine it rate of range expansion, 3) determine what clonal genotype(s) exist in PA, 4) determine how the abundances of the snail related to water chemistry, and 5) determine if the PA population differs in behavior from other invasive New Zealand mud snail populations. We surveyed streams in central PA for the New Zealand mud snail noting the relative abundance when found and measured the Calcium concentration, conductivity, and pH at each site from 2014-2016. We utilized allozyme electrophoresis to genotype the snail. We conducted behavior experiments comparing the PA population to other introduced and non-introduced populations with regard to their geotactic and photokinetic behaviors, which are known to influence the probability of predation.
We found that the snail appears to be thus far limited to the Spring Creek watershed, although it has slightly expanded its range and increased its abundances at several locations within that watershed in the past three years. The genotype of the PA population matches the most common clone in the US west and appears to prefer waters with higher conductivities and calcium concentrations. In comparing the PA population to other introduced and non-introduced populations, it behaves most similarly to its matching genotype in the western US, but some differences in behavior exist.