Adaptive variation in palp and gill size of the zebra mussel (<i>Dreissena polymorpha</i>) and Asian clam (<i>Corbicula fluminea</i>)

Abstract

Significant interpopulation differences occur in palp to gill area ratios of two nonindigenous species of freshwater bivalves in North America, Dreissena polymorpha and Corbicula fluminea. Larger palps (both species) and smaller gills (C. fluminea) occur in individuals from habitats characterized by a relatively high suspended solids concentration. The extremely brief evolutionary history of both species in North America is strong evidence that these differences in palp to gill area ratios are ecophenotypic.