Orbacz and Gaffney: Genetic stucture of Tautoga onitis 



343 



Additionally, this study shows that DGGE-hetero- 

 duplex analysis is a powerful technique that makes 

 it possible to screen large numbers of samples and 

 to identify haplotypes that differ by as little as a 

 single nucleotide. The unique tautog cytochrome b 

 haplotypes identified by DGGE-heteroduplex analy- 

 sis result from single base substitutions that would 

 not have been revealed by a RFLP analysis because 

 of the lack of restriction enzyme target sequences 

 spanning the mutation sites. 



The low level of genetic variation in the tautog 

 mitochondrial genome suggests that further mtDNA 

 analyses would likely prove to be unsuccessful in 

 delineating tautog population structure. It might 

 be more productive to focus instead on highly vari- 

 able nuclear DNA sequences such as microsatellite 

 loci, major histocompatibility complex genes, and 

 introns. In addition, more thorough tagging studies 

 and observations of tautog egg and larval transport 

 should prove valuable in determining the amount of 

 exchange among regions within the species range. 

 However, until further studies are undertaken, the 

 null hypothesis that tautog populations between 

 Rhode Island and Virginia constitute a single genetic 

 stock cannot be rejected. 



Acknowledgments 



This work was performed in partial fulfillment of the 

 requirements for the M.S. degree at the College of 

 Marine Studies, University of Delaware. We thank 

 John Graves and Timothy Targett for their help 

 in project design, execution, and analysis. Labora- 

 tory assistance was kindly provided by Ami Wilbur 

 and Thomas Lankford. This research was funded by 

 NCAA Saltonstall-Kennedy Project NA46FD0329 to 

 PMG. 



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