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Fishery Bulletin 100(4) 



to identify hybridization between C. fulva and P. furcifer. 

 With this enzyme, however, C. cruentata had a unique al- 

 lele and was thus eliminated as a putative parent for the 

 hybrid individuals. 



Mitochondrial DNA 



Allelic differences between C. fulva and P. furcifer were 

 found in all three mitochondrial gene regions. The ATPase 

 6 region was screened with six enzymes, one of which, Dde 

 I, showed differences between C. fulva, P. furcifer, and 

 C. cruentata (Tables 3 and 6). The 12S/16S region was 

 screened with seven enzymes. Two of these. Ban II and Rsa 

 I, demonstrated differences between C. fulva, P. furcifer, 

 and C. cruentata. The ND4 region was screened with nine 

 restriction enzymes, four of which (BstO I, Hpa II, Mbo I, 

 and Rsa I) showed differences between the species; mtDNA 

 composite haplotypes were unique to each species (Table 

 8). All 15 putative hybrids in the study had a composite 

 haplotype matching the common haplotype of C. fulva, 

 indicating that it was the maternal parent for all hybrid 

 individuals. Three Epinephelus guttatuf! specimens were 

 screened at the ND4 and ATPase 6 regions and showed a 

 unique composite haplotype; therefore this species was not 

 included in the study as a putative parent species. 



Discussion 



Morphological analysis 



In most cases, Fj hybrids should be morphologically 

 intermediate to the parent species and have low variation 

 within characters among themselves. Backcross individu- 

 als, because of random sorting of chromosomes, should 

 have higher variation within intermediate characters and 

 could fall anywhere in the morphological range of the pure 

 parent species (Anderson, 1949). In a principal component 

 analysis plot, a backcross hybrid's score would be expected 

 to be closer to the parent species to which the hybrid 



backcrossed, whereas an Fj hybrid's characters would be 

 expected to be in the center, closer to an average of the 

 scores of the parent species. 



A plot of the second principal component of the morpho- 

 logical analysis and the first factor of the meristic analysis 

 (Fig. 2) shows that C. fulva and P. furcifer are well segre- 

 gated according to morphological characters. The putative 

 hybrid individuals were clustered in between the parent 

 species. The post-Fj hybrid detected by using genetic anal- 

 yses, indicated by an arrow in Figure 2, clustered with the 

 putative Fj hybrid individuals. 



Genetic analyses 



Results of the allozyme analysis also supported hybridiza- 

 tion between C. fulva and P. furcifer in Bermuda. The puta- 

 tive hybrids were heterozygous at four distinguishing loci, 

 with the exception of two individuals that were homozygous 

 at one diagnostic locus each. One individual was homozy- 

 gous at the LDH-B* locus for the *75 allele. All twenty-eight 

 P. furcifer were homozygous for this same allele, indicating 

 hybrid backcrossing to P. furcifer. Another hybrid individual 

 was homozygous at the FH* locus for the *90 allele. The 

 40 C. fulva sampled in this study were homozygous for 

 this allele, suggesting hybrid backcrossing to C. fulva. This 

 hybrid individual was among those included in the morpho- 

 logical study and, as shown in the principal component plot 

 (Fig. 2). was morphologically the most similar to C. fulva. 

 It was not possible to distinguish F,, hybrids and backcross 

 hybrid individuals and henceforth the two individuals 

 described above are referred to as post-Fj hybrids. Because 

 all members of the presumed parent samples were homozy- 

 gous at all loci for diagnostic alleles, there was no evidence 

 of introgression between C. fulva and P. furcifer. 



The nuclear intron data were consistent with the allo- 

 zyme data and supported the hypothesis of hybridization 

 between C. fulva and P. furcifer. Because all hybrid indi- 

 viduals were heterozygous, post-F, hybridization was not 

 evident at these loci. Alleles present at both nuclear DNA 

 loci were unique between parent species and there was no 

 indication of introgression between these species. 



The mtDNA data clearly showed that C. fulva was the 

 maternal parent for all putative hybrids, including the two 

 post-Fj hybrids. This finding suggests a strong gender bias 

 in hybridization. All C. fulva had composite haplotypes quite 

 distinct from those of P. furcifer, and there was no evidence 

 of mtDNA introgression between the two parent species. 



Overall, the genetic and morphological analyses sug- 

 gest that all but two of the 15 putative hybrids were F, 

 individuals representing first generation hybridization 

 between a female C. fulva and a male P. furcifer (Table 9). 

 The occurrence of two post-F, hybrids indicates that Fj 

 hybrids are fertile, and the genotypes of the two post-Fj 

 hybrids demonstrate that F, hybrids can backcross with 

 either parent species. 



Hybridization in Bermuda 



Hybridization between C. fulva and P. furcifer is known 

 from only certain localities in the tropical Atlantic, despite 



