Abstract

We examined variation in mitochondrial (mt)DNA among samples of red snapper (Lutjanus campechanus) and red grouper (Epinephelus morio) from localities in the northern and western Gulf of Mexico. In both species, mtDNA haplotype frequencies were homogeneous between or among samples and there was no evidence of phylogeographic structure of haplotypes. In red snapper where multiple samples were examined, rare haplotypes were not clustered geographically and spatial autocorrelation of common haplotypes did not differ significantly from those expected when no correlation exists. These results are consistent with the hypothesis that gene flow between or among localities in both species is essentially continuous. The sedentary nature of juveniles and adults of both species suggests that gene flow may occur via hydrodynamic transport of pelagic eggs and larvae. Caveats to this hypothesis are considered. Levels of mtDNA variability, especially in red grouper, are among the lowest reported for marine fishes, and suggest minimally that genetic bottleneck events have occurred in the past or recent history of both species.

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