Assessing the probable distribution of the potentially invasive Chinese mystery snail, Cipangopaludina chinensis, in Nova Scotia using a random forest model approach

Non-native species that become invasive threaten natural biodiversity and can lead to socioeconomic impacts. Prediction of invasive species distributions is important to prevent further spread and protect vulnerable habitats and species at risk (SAR) from future invasions. The Chinese mystery snail, Cipangopaludina chinensis, native to Eastern Asia, is a non-native, potentially invasive, freshwater snail now widely established across North America, Belgium, and The Netherlands. This species was first reported in Nova Scotia, eastern Canada in 1955, but was not found to be established until the 1990s and now exists at high densities in several urban lakes. Nonetheless, the presence and potential distribution of this species in Nova Scotia remains unknown. Limited resources make it difficult to do a broad survey of freshwater lakes in Nova Scotia, however a species distribution probability model has the potential to direct focus to priority areas. We apply a random forest model in tandem with a combination of water quality, fish community, anthropogenic water use, and geomorphological data to predict C. chinensis habitat in Nova Scotia (NS), Canada. All predicted probabilities of suitable C. chinensisi habitats in Nova Scotia were > 50% and include Cape Breton Island, the Nova Scotia-New Brunswick border, and the Halifax Regional Municipality. Suitable habitats predicted for C. chinensis overlap with many SAR habitats, most notably brook floater mussel, Alasmidonta varicosa, and yellow lampmussel, Lampsila cariosa. Our results indicate that C. chinensis could become widespread throughout NS, appearing first in the aforementioned areas of highest probability. Further research is required to test C. chinensis ecological thresholds in order to improve the accuracy of future species distribution and habitat models, and to determine C. chinensis impacts on native freshwater mussel populations of conservation concern.