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Historical Biogeography of Sumatra and Western Archipelago, Indonesia: Insights from the flying lizards in the genus Draco (Iguania: Agamidae)

  • Author(s): Lawalata, Shobi
  • Advisor(s): McGuire, Jimmy A
  • et al.
Abstract

The island arc west of the island of Sumatra in Indonesia, here referred to as the Western Archipelago, is home to many endemic flora and fauna. Despite their importance in the biogeographic theater of insular Southeast Asia, little scientific attention has been given to these islands, with the exception of the four islands that comprise the Mentawai group. In this dissertation, I used the evolutionary history of the flying lizards in the genus Draco to elucidate the biogeographical history of Western Archipelago relative to its neighboring mega-island Sumatra. In Chapter 1, I provide an updated checklist of the herpetofauna of the islands in the archipelago--a list that had not been revisited or updated in the last 20 years. My visit to the islands of Western Archipelago proved to add considerably to our knowledge of the herpetofauna occurring in the area. In Chapter 2, I present a revision of the molecular phylogeny of the genus Draco by incorporating sequence data from nuclear markers. And finally, in Chapter 3 I looked at the phylogenetics and population genetics of the most widely distributed species of flying lizards in Sunda Shelf--Draco sumatranus the common flying lizards--to discern the historical process by which they colonized the islands of the Western Archipelago. Using one mitochondrial locus and nine nuclear loci, I employed phylogenetic and coalescent-based population genetic methods to reconstruct the evolutionary history of Draco sumatranus. My results suggest that the islands of Simeulue, Nias, Siberut, Sipora, North & South Pagai and Enggano are monophyletic, but the Batu and Banyak Islands themselves are more closely related to Northwest Sumatran populations. This divergence is inferred to have occurred ~550,000 years ago. These findings reject the hypothesis of independent overwater dispersal onto each island, and support the hypothesis that the Western Archipelago had been colonized via the Batu and Banyak Islands and was subsequently isolated by a vicariant event--most likely related to the Pleistocene changes in sea levels. I also uncovered deep divergences of Sumatran D. sumatranus populations that cannot be adequately explained simply by the emergence of the Sunda Shelf basin during the last glacial maxima, or the modern-day geography of the island. This hints at the cryptic diversity harbored within Sumatra, and merits a more rigorous study of the island's biogeography.

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