GENETIC IDENTIFICATION AND IMPLICATIONS OF ANOTHER INVASIVE SPECIES OF DREISSENID MUSSEL IN THE GREAT-LAKES

In this paper we report the discovery and implications of a second nonindigenous species of dreissenid mussel in the Great Lakes. This species was detected in a routine screening of zebra mussels (Dreissena polymorpha) for allozyme variability. The two species differ at allozyme loci (Nei's l = 0.30 using 12 loci) and in their shell morphology (the second species lacks the acute angle, or carina, between the ventral and dorsal surfaces of the shell of the zebra mussel). As a working name, at least until its species identity is discovered, we have called the new species the "quagga mussel." Currently, this mussel occurs in Lake Ontario in equal frequencies with D. polymorpha. Its low frequency of occurence in neighboring waters (e.g. the Erie canal, Niagara River, and outlet to Onondaga Lake) and lack of occurrence in any of the other Great Lakes suggest that (1) its point of introduction to North America was in Lake Ontario and (2) its range may expand.