INTRASPECIFIC VARIATION IN THE 16S RIBOSOMAL GENE OF CRASSOSTREA-VIRGINICA

Population structure was examined in Crassostrea virginica from Pamlic o Sound, North Carolina, and Chesapeake Bay, Virginia, on the Atlantic Coast and Galveston Bay, Texas, in the Gulf of Mexico. Haplotypes wer e identified by digesting with 10 restriction enzymes a 560-bp fragmen t of the mitochondrial 16S ribosomal gene amplified by polymerase chai n reaction (PCR). Restriction fragment profiles disclosed few differen ces: most C. virginica were the same haplotype, and 10 other rare hapl otypes showed no population or geographic structuring. As previous stu dies had established that little gene flow occurs between C, virginica on the Atlantic Coast and the Gulf of Mexico, it was concluded that f unctional constraints have prevented divergence in the restriction fra gment sites of the 16S ribosomal gene.