Ecological Risk Screening Summary - Spike-topped Applesnail (Pomacea diffusa) - Uncertain Risk

Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.

Pomacea diffusa, Spike-topped Applesnail, is a mollusk that is native to tropical and subtropical South America. P. diffusa is found in freshwater rivers, streams, ponds, and wetlands. It has a low tolerance to colder water but can live for several years under appropriate conditions. These applesnails are sold as both aquarium pets globally and as a food source in several countries. P. diffusa is often misidentified and sold in the aquarium market under the name P. bridgesii due to the historic taxonomic relationship between the species. Pomacea diffusa is regulated in six U.S. states. It has been introduced and established populations in the United States, Africa, Asia, and Australia. Mechanisms for potential impacts from introductions have been investigated in the laboratory but no information on documented impacts was found. The History of Invasiveness for Pomacea diffusa is classified as Data Deficient. The climate matching analysis for the contiguous United States indicates establishment concern. Areas of high match were found in the southern United States, primarily along the Gulf and Southern Atlantic Coasts. More northern areas and much of the west had low climate matches. The Certainty of Assessment for this ERSS is classified as Low due to the taxonomic history of P. diffusa being considered a subspecies of P. bridgesii and much of the historic information being reported under that name. The Overall Risk Assessment Category for Pomacea diffusa in the contiguous United States is Uncertain.