Population Structure of Island-Associated Spotted Dolphins: Modeling Gene Flow and Dispersal in Island Systems

EPA Grant Number: MA916975
Title: Population Structure of Island-Associated Spotted Dolphins: Modeling Gene Flow and Dispersal in Island Systems
Investigators: Courbis, Sarah
Institution: Portland State University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2008 through August 31, 2011
RFA: GRO Fellowships for Graduate Environmental Study (2008) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


The objective of this research is to address several environmental problems. One is the assumption that island-associated populations of dolphins have no restrictions on dispersal and gene flow. When dolphins are managed as single stocks (as they are in the Hawaiian Islands) when they are really multiple breeding stocks, levels of take, including harassment, hunting, and fisheries interactions, may be allowed that will reduce genetic diversity in the species. Human activities such as habitat destruction, pollution, run-off, etc. may not be controlled in some areas that have small, resident populations of animals, potentially removing or depleting these populations. Another problem my research addresses is our inability to predict dispersal and gene flow among island-associated dolphin populations, particularly those that are elusive, threatened, or endangered. Comparing my study with those of other island-associated dolphins (such as bottlenose dolphins (Tursiops truncatus) and spinner dolphins (Stenella longirostris)) and exploring niches, oceanographic features, and life history characteristics that vary among these dolphins will create insight into how to predict gene flow patterns and model dispersal. A third problem that my research addresses is the lack of a large scale comparison of populations of a ubiquitous dolphin species to explore evolution and radiation of such a species throughout the Pacific and Atlantic Oceans. This information will create a more "big picture" concept of how dolphins radiate, disperse to new habitats, and develop genetic barriers in the absence and presence of physical barriers. Finally, on a finer scale, my research will provide information specifically for management and conservation of spotted dolphins in the Hawaiian Islands.


I am collaborating with Cascadia Research Collective and the National Marine Fisheries Service (NMFS) and cooperating with other agencies and universities. I am using genetic and photo-identification techniques to explore dispersal and gene flow of spotted dolphins (Stenella attenuata) near the main Hawaiian Islands. I am also exploring intra-group relatedness by comparing genetic sequences among dolphins sampled together in single groups. In addition, I am using data from previous studies in the Pacific and Atlantic to explore evolutionary relationships among spotted dolphins and other Stenella. Further, I am using photo-identification to estimate population sizes and association patterns.

Expected Results:

I hypothesize that island populations of dolphins exhibit genetic differentiation among island areas that is mediated by female philopatry. If my hypothesis is true, my data will show significant mtDNA differentiation among island areas, in some cases enough to consider designating populations as separate genetic stocks. I expect different dominant haplotypes at different island areas. Also, mtDNA differentiation will be higher for females than corresponding males, while microsatellite population differentiation will be similar when analyzed separately by sex. I expect that photo-identification will show few or no inter-island re-sightings among island areas that show genetic differentiation.

Supplemental Keywords:

spotted dolphin, genetics, photo-identification, population structure, conservation, Hawaiian Islands, Stenella,

Progress and Final Reports:

  • 2009
  • 2010
  • Final