Large Differences Over Small Distances: Plasticity in the Shells of Elimia potosiensis (Gastropoda: Pleuroceridae)

Phenotypic plasticity in freshwater mollusks is a well-known phenomenon, occurring in both bivalves and gastropods. Most work on freshwater snail plasticity has focused either on presence/absence of a single factor, or has looked at responses to environmental gradients over large geographical scales. Using the pleurocerid snail Elimia potosiensis from a spring and creek in Arkansas, we show a plastic environmental response at a scale thousands of times smaller than was previously known. Shells of E. potosiensis exhibit plasticity consist with that seen in other pleurocerids over the course of hundreds of meters. Possible explanations for this small-scale plasticity are offered.