Date of Award

2001

Embargo Period

1-1-2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular and Cellular Biology and Pathobiology

College

College of Graduate Studies

First Advisor

Robert W. Chapman

Second Advisor

Jon Ahlquist

Third Advisor

Paul Sandifer

Fourth Advisor

Yuko Y. Palesch

Fifth Advisor

Elizabeth Wenner

Sixth Advisor

Greg Warr

Abstract

Litopenaeus setiferus, Atlantic white shrimp, is a commercially and recreationally valuable species, yet little is known of its population structure. Litopenaeus setiferus are found along the Atlantic coast from New York to St. Lucie, Florida, and from the Ochlockonee River on the Gulf coast of Florida to Campeche, Mexico. Gulf and Atlantic populations probably separated sometime during the last deglaciation period (10,000 to 20,000 years ago). In addition, the extensive freshwater ourflow of the Mississippi River may provide a physical barrier to gene flow, and concentrations of shrimp in Tabasco and Campeche Bay, Mexico, are thought to form a separate stock from those found in Texas. Microsatellite genetic markers were chosen for a population genetic analysis of L. setiferus. Six microsatellite loci, three containing the dinucleotide repeat (GT) and three containing tri- or tetranucleotide repeats, were identified. Shrimp were collected from North Carolina, South Carolina (over a period of four years), Georgia, Atlantic and Gulf coasts of Florida, the Mississippi River Delta (over a period of two years) and west of the Mississippi River Delta in Louisiana, Texas, and Mexico. DNA was isolated from these individuals and all six microsatellite loci were assayed. These loci were for the most part highly polymorphic with an average expected heterozygosity of 0.68. Deviations from Hardy-Weinberg proportions were observed over all samples, but the presence of null alleles confounded any biological interpretation of this result. Tests of the similarity of allele frequency distributions and distance measure analyses showed occasional indications of random geographic and temporal differentiation superimposed over broad scale genetic homogeneity. FST and RST calculations confirmed that most genetic variation was contained within samples. The large-scale genetic homogeneity observed is a probable consequence of either ongoing gene flow among these samples or a recent separation, while the local genetic differentiation is consistent with genetic sampling. Conservative management of this species requires consideration of the probabilities that these shrimp are mixing across state and federal boundaries; that the number of migrants may not replenish a depleted stock; and that overfishing may affect the genetic integrity of the stock.

Rights

All rights reserved. Copyright is held by the author.

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