Invasive New Zealand Mud Snail Populations Respond Differently to a Common Pesticide

The New Zealand mud snail (Potamopyrgus antipodarum) is a world-wide invader in freshwater and brackish water systems. Recent results demonstrate substantial variation between populations in traits such as dispersal ability, predator avoidance behaviors, and resistance to desiccation. Here we compare different North American populations of this snail with respect to their tolerance to the commonly used insecticide malathion. Snails were exposed to concentrations of the pesticide ranging from 0 mg/L to 500 mg/L for 48 hours and then returned to untreated water. The data suggests that malathion concentrations above 50 mg/L result in significant mortality. There were significant differences between invasive populations in their responses to the pesticide. This demonstrates that there is likely to be genetic variation in this trait between populations, and that there is potential for this species to evolve to increase resistance to this pesticide if it is exposed to it.