Genetic diversity in the mtDNA control region and population structure in the pink shrimp Farfantepenaeus duorarum

The pink shrimp (Farfantepenaeus duorarum) is an ecologically and economically important penaeid species in the southeastern United States. The biological and economic importance of this species prompted us to conduct a molecular genetic assessment of pink shrimp genetic diversity and population genetic structure. We sequenced a 558-base portion of the mitochondrial DNA (mtDNA) control region from pink shrimp collected at five locations ranging from North Carolina to south Texas. Haplotype and nucleotide diversity values in pink shrimp are among the highest yet reponed for decapods. In our samples, all haplotypes were unique, and the average nucleotide diversity was approximately 2%. Nucleotide divergence between haplotypes ranged 0.2-3.9%. A mismatch analysis produced a unimodal distribution of pairwise differences between haplotypes that is consistent with a historic rapid population expansion. A population expansion, high mutation rate in the control region, and large population size all probably contributed to the development of high genetic diversity. This level of genetic diversity suggests that the mtDNA control region might be useful as a genetic marker in peneaid shrimp used for aquaculture. We detected no population differentiation, suggesting that long-term dispersal and gene flow are high enough to maintain a genetically homogeneous population structure over the geographic distances used in this analysis. The continuous distribution and high numbers of pink shrimp around south Florida likely have contributed to the genetic homogeneity observed in pink shrimp inhabiting the Atlantic Ocean and Gulf of Mexico. These data provide a baseline from which the genetic diversity and population structure of pink shrimp, which are highly exploited and vulnerable to the varied impacts of regional shrimp aquaculture, can be appraised in the future.