DNA microsatellite loci and genetic structure of red snapper in the Gulf of Mexico

Five polymorphic microsatellite loci were developed from genomic DNA of red snapper Lufjanus campechanus and used to evaluate genetic variation among 194 red snapper sampled from three locations in the northern Gulf of Mexico and one location off the northern Yucatan Peninsula in Mexico. From 5 to 13 alleles were observed per locus, and expected heterozygosities ranged from 0.143 to 0.779. No significant departures from expectations of Hardy-Weinberg equilibrium were found at any locus either within samples or when samples were pooled across localities. Locus-by-locus tests of allele-frequency homogeneity over the four localities were nonsignificant. Weir and Cockerham's Theta at each locus ranged from -0.003 to 0.012, and Statkin's R-ST at each locus ranged from -0.014 to 0.008. None of the estimates of Theta and R-ST differed significantly from zero, and magnitudes of Theta and R-ST did not appear to vary with geographic distance between localities. These results are consistent with the hypothesis that red snapper at these localities constitute a single population. There are, however a number of caveats to this hypothesis. Detection of population structure of red snapper in the Gulf of Mexico may require more samples and larger sample sizes, and the importance of local reproduction to recruitment needs to be investigated via examination of larvae settling onto reefs. A positive but nonsignificant correlation existed between mean number of repeat units per microsatellite allele and heterozygosity of the locus.