Herbivory on aquatic vascular plants by the introduced golden apple snail (Pomacea canaliculata) in Lao PDR

The effect of naturally found densities of the exotic and herbivorous golden apple snail (Pomacea canaliculata) on three dominant aquatic plants - duckweed (Lemna minor), water hyacinth (Eichhornia crassipes) and morning glory (Ipomoea aquatica) - was assessed in a wetland survey and quantified in a field experiment in Laos in southeast Asia. Snail grazing reduced plant biomass, but plant species were differently affected by grazing. Duckweed had almost disappeared after 6 and water hyacinth after 21 days, whereas morning glory remained at 80% of initial biomass after 32 days. Snail growth was lowest on morning glory and, when all plant species were simultaneously presented to snails, this plant was not preferred. We suggest that the negative effect the golden apple snail had on the growth of these plant species in field enclosures is present in the natural environment as well. This new and intense herbivory could have serious negative effects on invaded freshwater ecosystems in this region.