RESUMO
Variation in mitochondrial DNA (mtDNA) was examined among 86 red snapper (Lutjanus campechanus) from three geographic localities in the northern Gulf of Mexico (Gulf). A total of 29 composite mtDNA genotypes (haplotypes) was found; one haplotype occurred in 39 of 86 (45.3%) individuals assayed, and 20 haplotypes occurred in only one individual each. Tests of heterogeneity in mtDNA haplotype frequencies among localities were not significant, and there was little evidence of phylogeographic structuring of mtDNA haplotypes. These findings are consistent with the hypothesis that red snapper in the northern Gulf comprise a single, panmictic population. The observed genetic homogeneity also indicates considerable gene flow (migration) among red snapper in the northern Gulf. Significant differences in levels of intrapopulational mtDNA variation were found among localities. Levels of intrapopulational mtDNA diversity in red snapper are low relative to other marine fish species studied to date.