666 



Fishery Bulletin 94(4), 1996 



Results 



Ten restriction enzymes produced an average 

 of 50 restriction fragments with a survey of 288 

 base pairs (bp) or 1.74% of the 16.6 kb mtDNA 

 molecule (Table 1). Seven haplotypes were de- 

 tected, resulting in a nucleon diversity of 0.640 

 and an overall nucleotide sequence diversity 

 (NSD) of 0.13% (Table 2; Fig. 2). Four of the ten 

 restriction enzymes revealed multiple restric- 

 tion patterns; one enzyme, Hpa I, detected four 

 different patterns. The single most common 

 haplotype was found with similar frequencies 

 in each sample and in each year within the At- 

 lantic sample (range=0.50-0.67), and three less 

 common haplotypes also occurred in all three 

 geographic samples. Three rare haplotypes, 

 each found in a different individual, were 

 equally divided among the three sampling loca- 

 tions. Each haplotype differed from the common 

 pattern by the gain or loss of a single restric- 

 tion site (Fig. 2.) The chi-square probability of 

 haplotype homogeneity among samples (Roff and 

 Bentzen, 1989) was 0.694, indicating that the 

 samples could have been drawn from a single popu- 

 lation of mtDNA haplotypes. The nucleotide sequence 

 divergences between the three samples, corrected for 

 within sample diversity, were all less than 0.01%. 



Discussion 



The results of this study indicate that historically 

 there has been sufficient gene flow among sharpnose 



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Virginia 

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 5 

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 23 



Texas 

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Veracruz 

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Figure 2 



Composite mtDNA haplotypes, inferred phylogenetic relation- 

 ships among haplotypes (vertical hatches represent restriction 

 site differences), and distribution of haplotypes in samples of 

 Atlantic sharpnose shark, Rhizoprionodon terraenovae. Compos- 

 ite haplotypes consist of restriction fragment patterns for the fol- 

 lowing enzymes (left to right): Ava I, Ava II, Ban I, Bel I, BstE II. 

 Dra I, Hmd III, Hpa I, Sea I, and Xho I. 



