Date

2005

Document Type

Master's Thesis

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

The family Alopiidae is comprised of three species: the pelagic (Alopias pelagicus), bigeye (A. superciliosus), and common (A. vulpinus) thresher sharks. Alopias pelagicus occurs only in the Indian and Pacific Oceans, while the other two species are distributed worldwide. Despite growing conservation concerns, genetic relatedness among thresher shark populations is poorly known. I examined the phylogeographic structure of each species using DNA sequences from the mitochondrial control region. Alopias samples were collected from the East and West coasts of the United States, Gulf of Mexico, Gulf of California, Clipperton Atoll, Guatemala, Ecuador, Hawaii, Taiwan, Indonesia, New Caledonia, New Zealand, South Africa and France. Despite their high dispersal potential, my data indicate limited gene flow among thresher shark populations, but phylogeographic patterns differ among species. Gene flow in A. pelagicus is limited across the Pacific Ocean, but is extensive among locations in both the eastern and western Pacific. In A. superciliosus, shallow population structure was detected among samples from Indo-Pacific and Atlantic populations, but not among specimens taken from locations spanning the Indo-Pacific Ocean. Results for A. vulpinus indicate genetic heterogeneity among almost all sampled populations, both within and between the Atlantic and Indo-Pacific oceans. Taken together, my data suggest that intraspecific biological and ecological differences among thresher sharks may be sufficient to cause variable patterns of interspecific genetic population structure. This study also highlights the need for international cooperation for the conservation and management of thresher sharks.

Comments

Thesis (M.S.) Division of Science and Environmental Policy. Moss Landing Marine Laboratories

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