Seyoum et al. Genetic population structure in Saaenops ocellatus 



131 



by region (Atlantic or Gulf) 

 and for all samples combined. 

 The statistical significance of 

 the association was tested by 

 random permutation analysis 

 by using 500 replicates (Sokal 

 andRohlf, 1995). 



Results 



-AP 



FB 



■-OF 



c 



CH 



TB 



■SA 



Gulf 



r-SC 



54 



We analyzed sequence data 

 from a 369-bp portion of the 

 mtDNA control region for 209 

 red drum. A total of 81 poly- 

 morphic sites were observed 

 among all individuals. Of 

 these, 67 sites had single- 

 state, 11 had double-state, and 

 3 had triple-state transfor- 

 mations, totaling 98 polymor- 

 phisms and including two 

 indels. The first indel consisted 

 of an insertion of a pyrimidine 

 (T or C) at position 160 and 

 occurred in 10 individuals; the 

 second indel consisted of a 



deletion of a purine (A) at position 210 and occurred 

 in one of these individuals (Table 1). Seventy-three 

 of the substitutions were TSs and 22 were TVs. As 

 with control regions of other fishes (Stepien, 1995), 

 the relative frequencies of the four nucleotide bases 

 differed; adenine was the most prevalent (399^), fol- 

 lowed by thymine (27*^), cytosine(23'^), and guanine 

 (11%). The TSrTV ratio was 3.4:1 and was similar 

 to ratios reported for marine and freshwater fishes 

 (Stepien, 1995; but see Brown et al., 1993). 



We observed 134 different haplotypes in the 209 

 individuals sequenced (Table 1). Sequences of these 

 haplotypes have been deposited in GenBank under 

 the accession numbers AF054672-F054805. Twenty- 

 nine haplotypes were shared by more than one indi- 

 vidual. Two haplotypes, no. 56 and no. 83, were 

 shared by nine and nineteen individuals, respectively, 

 which were widely dispersed among seven samples. 

 Twenty-six haplotypes occurred infrequently, 25 in 

 two to five individuals scattered among two to five 

 samples, and one in two members of a single sample. 

 Of the 19 individuals with haplotype no. 83, 17 were 

 from the Atlantic and two from the Gulf The per- 

 centage of different haplotypes in any one sample 

 varied from im to lOO'/f {x=Sl'7c ). Haplotype diver- 

 sity within samples ranged from 0.95 to 1.00 (x=0.98, 

 SE=0.00) and nucleotide diversity ranged from 0.025 

 to 0.037 (x=0.030, SE=0.003). 



i-IR 



4 



ML 

 PO 



•-TP 



Atlantic 



1 



0,36 



0.18 



000 



Patristic distance  100 



Figure 2 



Neighbor-joining tree based on mtDNA nucleotide divergence between samples of red 

 drum from Florida and South Carolina nearshore waters. Sample location and abbrevi- 

 ates are defined in Figure 1. 



Percent sequence divergences between pairs of dif- 

 ferent haplotypes ranged from 0.3% to 7.1% (x- 

 3.2%; SE=0.oi7). Between any two different haplo- 

 types, the number of nucleotide differences varied from 

 one to 26 (x=\2). The topology of the unrooted tree 

 neighbor-joining (not shown) revealed that the 134 

 haplotypes were not phylogeographically structured. 

 Haplotypes observed in Gulf and Atlantic samples were 

 scattered throughout the tree; with the exception of 

 two terminal groupings, nodes on the tree had low sta- 

 tistical support. Internal branch lengths of the tree 

 were generally short; however, one interior branch was 

 relatively long, and it defined the only well-supported 

 major clade (bootstrap value=85). This clade consisted 

 of 23 haplotypes, including the 10 haplotypes that had 

 the insertion at position 160. The 10 insertion-bearing 

 haplotypes were found in nine Atlantic individuals but 

 in only one Gulf individual. 



The D values between pairs of samples ranged 

 from -0.08% to 0.10%. In the neighbor-joining clus- 

 ter analysis, cohesion of the samples within geo- 

 graphic regions was generally observed (Fig. 2). All 

 Atlantic samples formed a distinct clade which was 

 separated by the longest branch of the tree from the 

 clade formed by the Gulf samples. Less cohesion was 

 observed among the Gulf samples, although the geo- 

 graphically proximal SA, TB. and CH samples clus- 

 tered closely together. 



