ABSTRACT
Similarities in autecology and niche overlap of the zebra mussel (Dreissena polymorpha) and a congener, the quagga mussel (Dreissena rostriformis bugensis), predict the potential for strong interspecic competition. During the initial invasion of dreissenids in North America, the zebra mussel dominated; however, subsequently quagga mussels essentially replaced zebra mussels and are now the dominant dreissenid in many benthic habitats. While the range and population densities of quagga mussels increased slowly in North America, this species extended its range faster in the western portions than in the eastern portions of the United
States. This chapter reviews studies of abiotic and biotic factors that affect competitive interactions between quagga and zebra mussels.
