Feeding rates of an introduced freshwater gastropod Pomacea insularum on native and nonindigenous aquatic plants in Florida

Pomacea insularum (Gastropoda: Ampullariidae) is a common, nonindigenous species in many parts of the world and an important consumer of aquatic macrophytes. We conducted laboratory trials to quantify the rates of consumption of native and nonindigenous aquatic plants in Florida, where this snail has been introduced. Twenty-two freshwater plant and alga species were presented to naive P. insularum in laboratory trials, using single-snail replicates and simultaneous (no-snail) controls. Pomacea insularum damaged > 50% of the replicate plants of 16 species; for 14 of these we calculated ash-free dry weight-specific feeding rates of P. insularum. The most heavily consumed plants were two native species: Limnobium spongia (0.744 g/g/d) and Chara sp. (0.478 g/g/d). Nonindigenous Panicum repens (0.306 g/g/d), Hydrilla verticillata (0.292 g/g/d) and Ceratophyllum demersum (0.254 g/g/d); and native Sagittaria latifolia (0.257 g/g/d), Najas guadalupensis (0.225 g/g/d) and Vallisneria americana (0.207 g/g/d) were also heavily consumed. Nonindigenous Eichhornia crassipes was consumed at a lower rate (0.053 g/g/d) while nonindigenous Colocasia esculenta and Pistia stratiotes were not consumed at detectable levels. Our results suggest that P. insularum cannot be relied upon as a biological control agent for nonindigenous plants and may heavily impact native macrophytes.