Testing for Population Structure in Striped Marlin, Tetrapturus audax, Using Both Mitochondrial and Nuclear Markers

EPA Grant Number: F5E20953
Title: Testing for Population Structure in Striped Marlin, Tetrapturus audax, Using Both Mitochondrial and Nuclear Markers
Investigators: Purcell, Catherine
Institution: University of Southern California
EPA Project Officer: Lee, Sonja
Project Period: August 22, 2005 through May 12, 2006
Project Amount: $102,530
RFA: STAR Graduate Fellowships (2005) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


In this study, striped marlin (Tetrapturus audax) are used to examine population genetic structure in a highly migratory species. Due to structuring already seen in this organism, they can be used to address important questions such as:

  1. Is the structure temporally stable? Many population studies have provided a snapshot of what populations are doing at a particular point in time, however temporal variation has proven to be an important component in the genetic subdivision of other taxa.
  2. What is the mechanism creating or maintaining this structure? Specifically, this study will investigate spawning site fidelity as the potential underlying mechanism.
  3. Do other markers or loci reveal the same pattern? Differences among markers can be informative, and can reduce the potential for erroneous signals of limited gene flow.


This project will estimate population subdivision using both mitochondrial and nuclear DNA markers. PCR is used to amplify the mitochondrial control region, which is then sequenced to detect subtle genetic structuring. Nuclear microsatellites are used as another measure of subdivision, and as a measure of heterogeneity within and among populations. Because mitochondrial DNA is maternally inherited and microsatellites are biparentally inherited, comparisons between these two markers may help determine whether the population genetic structure is sex-specific. A concurrent sampling scheme will be employed to collect adult tissue from 7 locations representative of their range in the Pacific: Mexico, Ecuador, Southern California, Hawaii, Japan, Australia and New Zealand. This repeat sampling will be conducted over the course of 3 years to test for temporal stability among locations. Larval samples are also being collected in this study in known spawning locations using plankton tows. Larvae and adults will be analyzed with the same molecular techniques.

Expected Results:

This project is highly consequential for the future of striped marlin, as the results from this study can be directly used to create more effective management plans to protect this species. As a commercially and recreationally important species within the Pacific, preservation of this resource is vital to all those who depend on this fishery. Additionally, a better understanding of the cause of the population structure in striped marlin could be crucial to comprehending variation between superficially similar pelagic species, and may contribute to a re-evaluation of the level of diversity present in the oceans.

Supplemental Keywords:

temporal variation, striped marlin, billfish, gene flow, spawning site fidelity, genetic structure, mitochondrial DNA, control region, microsatellites, larvae, Tetrapturus audax, fisheries, sustainable resources, stock structure, management, pelagic species, diversity, biodiversity, population structure, population subdivision, molecular markers, migration, migratory species, conservation, conservation biology,, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Habitat, Environmental Monitoring, Ecology and Ecosystems, habitat dynamics, fish, habitat use, animal responses, Marlin, mitochondrial marker, spatial ecology, conservation biology, breeding habitat, genetic markers, habitat population structure

Progress and Final Reports:

  • Final