Diagnostic genetic markers and evolutionary relationships among invasive dreissenoid and corbiculoid bivalves in North America: Phylogenetic signal from mitochondrial 16S rDNA

Diagnostic genetic markers from 486 aligned nucleotide sequences of mitocho ndrial 16S ribosomal DNA were developed for the four closely related specie s of dreissenoid and corbiculoid bivalves that have invaded North America; the zebra mussel Dreissena polymorpha, the quagga mussel D. bugensis, and t he dark false mussel Mytilopsis leucophaeata of the superfamily Dreissenoid ea, and the Asian clam Corbicula fluminea of the sister superfamily Corbicu loidea. Evolutionary relationships were examined among the four genera and comparisons were made with native Eurasian populations of D. polymorpha and D. bugensis. Tests were conducted for gender-specific mitochondrial lineag es, which occur in some other bivalves. Genetic variability and divergence rates were tested between stem (paired) and loop (unpaired) regions of seco ndary structure. There were 251 variable nucleotide sites, of which 99 were phylogenetically informative. Overall transition to transversion ratio was 0.76: 1.00 and both accumulated linearly in stem and loop regions, suggest ing appropriate phylogenetic signal. Genetic distance calibration with the fossil record estimated the pairwise sequence divergence as 0.0057 +/- 0.00 04 per million years. Mytilopsis and Dreissena appear to have diverged abou t 20.7 +/- 2.7 million years ago. D. bugensis and D. polymorpha appear sepa rated by about 13.2 +/- 2.2 million years. No intraspecific variation was f ound, including between Eurasian and North American populations, among shal low and deep morphotypes of D. bugensis and between the sexes. Restriction endonuclease markers were developed to distinguish among the species at all life history stages, allowing rapid identification in areas of sympatric d istribution. (C) 1999 Academic Press.