Pleistocene sea level fluctuations and the phylogeography of the dugong in Australian waters

Authors

  • David Blair,

    Corresponding author
    1. School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
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  • Adrian McMahon,

    1. School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
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  • Brenda McDonald,

    1. School of Marine and Tropical Biology and School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, Australia
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  • Daniela Tikel,

    1. School of Marine and Tropical Biology and School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, Australia
    Current affiliation:
    1. Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, Queensland, Australia
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  • Michelle Waycott,

    1. School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
    Current affiliation:
    1. Plant Biodiversity Centre, Department of Environment and Natural Resources, Adelaide, South Australia, Australia
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  • Helene Marsh

    1. School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, Australia
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Abstract

We investigated phylogeography, demography, and population connectivity of the dugong (Dugong dugon) in Australian waters using mitochondrial control region DNA sequences from 177 Australian dugongs and 11 from elsewhere. The dugong is widespread in shallow Indo-West Pacific waters suitable for growth of its main food, seagrass. We hypothesized that the loss of habitat and creation of a land barrier (the Torres Strait landbridge) during low sea level stands associated with Pleistocene glacial cycles have left a persisting genetic signature in the dugong. The landbridge was most recently flooded about 7,000 yr ago. Individual dugongs are capable of traveling long distances, suggesting an alternative hypothesis that there might now be little genetic differentiation across the dugong's Australian range. We demonstrated that Australian dugongs fall into two distinct maternal lineages and exhibit a phylogeographic pattern reflecting Pleistocene sea-level fluctuations. Within each lineage, genetic structure exists, albeit at large spatial scales. We suggest that these lineages diverged following the last emergence of the Torres Strait landbridge (ca. 115 kya) and remained geographically separated until after 7 kya when passage through Torres Strait again became possible for marine animals. Evidence for population growth in the widespread lineage, especially after the last glacial maximum, was detected.

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