Marine Science

Marine Science

Senior Theses 2003

Andrea K. Horntvedt (2003). Genetic differences between western Atlantic and eastern Pacific populations of the yellowtailed leatherjack, Oligoplites saurus
Faculty advisor: William Szelistowski


Oligoplites saurus, the yellow tailed leather jack, is one of few coastal marine bony fishes distributed both in the Western Atlantic and Eastern Pacific Oceans. The population genetic structure of this species is therefore particularly interesting. To determine the genetic differences between the Atlantic O. saurus saurus and Pacific 0. saurus inornatus, DNA sequencing and RFLP analysis of a portion of the 16s rRNA gene were used. Specimens were collected from three sites in the Western Atlantic (Caribbean, Gulf of Mexico and Atlantic), and one site from the Eastern Pacific. Results indicated no consistent base pair mutations among samples from the three Atlantic sites, and 10 bp mutations between Atlantic and Pacific samples, including 3 transversions and 7 transitions. Using a mitochondrial rRNA molecular clock rate of 0.14% transversion changes per million years, the age of separation is estimated at 7.44 MYA. This is compared to the geminate species pair Trachinotus kennedyi and T falcatus that only had 1 transversion and 6 transitions, and estimated to have diverged 2.58 MYA. The mutational differences and the predictions of the molecular clock support the hypothesis that Atlantic and Pacific populations of Oligoplites were separated at or before the rise of the Isthmus of Panama approximately 3.1-3.5 MYA. These results also suggest that the two populations should be considered separate species.

Student Research