Potential overwintering areas of the alien apple snail, Pomacea canaliculata, in Japan at its northern distribution limit

Abstract

For risk assessment and prevention of further invasion of the alien apple snail, Pomacea canaliculata, into new habitats in Japan, we estimated the snail’s potential overwintering areas on the basis of climate data and a field census. Presence or absence was examined at 38 sites in six regions of Kyushu Island, where the snail has invaded most areas in which it can overwinter. The effects of cumulative low temperature during winter on the presence/absence data were examined by using a logistic regression analysis. As a result, a model using cumulative low temperature below 10 °C (CLT10) was adopted as the best determinant of snail overwintering success, with the risk evaluation formula y = 1 / [1 + exp(–4.7931474 + 0.007574x)], where x is CLT10 (5-year average) and y is the probability of overwintering success. To verify the model, y was calculated for 1348 sites on Honshu, Shikoku, and Kyushu islands where P. canaliculata was confirmed to be present by recent field censuses. Of these sites, 1344 (> 99.7%) had y values exceeding 0.4; the remaining four had y values ranging from > 0.2 to 0.4, with a minimum of 0.377. These results indicate that the model can be used to predict the overwintering success and subsequent localization of P. canaliculata. A potential invasion map that we drew by using the model will help to prevent further expansion of this invasive snail into new areas.