Dolphin Population Genetics

Figure 1. Sampling locations in SW Western Australia.

Lead researcher

Collaborators

Supervisors

 

 

Background

Determining what constitutes a ‘population’ for management purposes requires an understanding of structure, i.e. the level of connectivity between individuals across their distribution. For example, a species distributed as a series of small, somewhat isolated population fragments will require different management to a species of the same total abundance, but which is structured as a single, well-connected population. Examining the structure of populations in the marine environment presents a particular challenge due to the absence of obvious barriers to gene flow, and the highly mobile nature of many marine species. To this end, genetic tools have been employed to address a variety of questions in mobile marine taxa, including marine mammals, providing key data to inform conservation and management strategies.

Indo-Pacific bottlenose dolphins (Tursiops aduncus) are the focal species of this research. Photo: Alex Brown.

Indo-Pacific bottlenose dolphins (Tursiops aduncus) are the focal species of this research. Photo: Alex Brown.

In this project, we use a variety of genetic tools to assess the genetic diversity, population structure, gene flow and dispersal of populations along the southwestern coast of Western Australia. These tools also allow us to determine the sex of individual dolphins, providing key information for behavioural studies (see Sprogis et al. 2016a) and understanding sex-specific population structure and dynamics (see Sprogis et al. 2016b, Manlik et al. 2016).

Specific objectives

  1. Identification of the species of dolphins in Bunbury and wider south western Western Australia.
  2. Assessment of genetic diversity.
  3. Determination of sex of individuals.
  4. Estimate the level of gene flow (mixing) between dolphin populations along the coast of southwestern Western Australia (Figure 1).
  5. Assessment of directional dispersal of dolphins along the coast.

Methods

Biopsy samples are collected from free-swimming dolphins using a purpose-built darting system (Paxarms; Krützen et al. 2002), which collect a small quantity (1-2ml) of skin and blubber for genetic analyses (Figure 2). All darting is conducted by trained operators with permits from the WA Department of Parks and Wildlife and Animal Ethics Committee approval. Once obtained, the samples are stored in vials for later analyses. In addition to extracting DNA for genetic analyses, tissue samples may also be used for food web and dietary studies (stable isotope and fatty acid signature analyses) and environmental and anthropogenic pollutant studies (contaminant analyses).

Sampling

Figure 2. Using a remote darting system to obtain tissue samples from free-swimming dolphins for genetic and other analyses. Studies have shown that this procedure causes a small wound which heals within 3 weeks, and dolphins show no long-term behavioural effects. Photos: Alex Brown (left); Simon Allen (right). 

In the lab, DNA is extracted from tissue samples. Sex-chromosome-specific genetic markers are used to determine the sex of individuals, and a Polymerase Chain Reaction (PCR) is used to amplify loci of interest. On the basis of genetic variants (‘genotypes’) we can identify species of dolphins, and in many cases even individual dolphins. We can also assess genetic diversity of the dolphins by analyzing adaptively neutral genetic markers (microsatellite loci and mitochondrial DNA) and immune genes of the major histocompatibility complex (MHC). Genetic diversity is important for populations to adapt to a continuously changing environment. We also combine genetic information and computer models to evaluate the level of structure within the sampled population and direction of past migration patterns. Knowing which populations act as sink or source population is important in order to evaluate metapopulation dynamics. For example, a declining population can potentially be rescued if individuals of other populations migrate into that population.

Relevant publications

Contact Us

We're not around right now. But you can send us an email and we'll get back to you, asap.