Phylogeography of Gracilaria salicornia (C. Agardh) E. Y. Dawson & Hypnea pannosa J. Agardh in the Wallacea Region

  • Abdul Razaq Chasani

    Student thesis: Doctor of Philosophy (PhD) - CDU


    As the global epicentre of marine biodiversity, the Indo-Australian Archipelago (IAA) and the Coral Triangle (CT), is one of the most evolutionary and biogeographically complex regions on Earth. While there has been a rapid increase in marine phylogeographic studies in the region, exploring connectivity, dispersal barriers and the evolution of species diversity – studies on benthic marine macroalgae are rare.

    This study examined major phylogeographic patterns in 2 common species of Rhodophyta, Gracilaria salicornia and Hypnea pannosa, within the IAA and CT region. Specifically, the influence of the Wallace’s Line (WL) on the distribution and connectivity of G. salicornia populations in the Pacific Ocean; the influence of the Indonesian Through Flow (ITF) in the isolation and genetic structuring of H. pannosa populations; and whether the center of diversification for G. salicornia populations is located in either, the marine biodiversity hotspots inside the CT, or in peripheral ecosystems. For G. salicornia, a total of 171 individuals from 8 populations and 195 individuals from 29 distinct localities were analysed, respectively, using the cox2-cox3 mtDNA and the rbcL-rbcS cpDNA sequencing markers. For H. pannosa, a total of 80 individuals from Indonesia and Australia were analysed using mtDNA cox1 and cpDNA rbcL DNA sequences.

    Study results indicate that the phylogeography of G. salicornia is likely a result of different past and contemporary processes promoting isolation and connectivity around the Makassar Straits and Lombok Straits – with the WL proved to be a porous barrier to gene flow for this particular species. Analysis also confirmed the monophyly of this species and supported the Center of Accumulation Model as the diversification mechanism for populations of G. salicornia in the Indo-Pacific Ocean. In H. pannosa, strong genetic structure was found across the IAA, particularly among populations from Indonesia, Ningaloo Reef, and the Great Barrier Reef and suggests the presence of a Sahul-Sunda genetic break between these three regions.
    Date of AwardDec 2017
    Original languageEnglish
    SupervisorKaren Edyvane (Supervisor)

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