Browsing by Author "Sithaldeen, Riashna"

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    Phylogeny and phylogeography of the Chacma Baboon (Papio ursinus): the role of landscape in shaping contemporary genetic structure in the southern African baboon
    (2011) Sithaldeen, Riashna; Ackermann, Rebecca Rogers; Bishop, Jacqueline
    This thesis contributes to our understanding of the role of climate and landscape change in structuring diversity within chacma baboons (Papio ursinus). The data set comprises molecular sequences from two mitochondrial DNA markers: the Brown region and the hypervariable D-loop. DNA was extracted from faecal samples of 261 free living chacma baboons across southern Africa. Phylogenetic and phylogeographic techniques, including coalescent modeling, were used to examine past and present population dynamics of chacma baboon populations. Bayesian tree constructions provide a timeline of diversification for the sample. Although the ecological drivers of ongoing differentiation remain unclear, it was shown that population contractions and expansions have also played a significant role in driving regional genetic structure within the species.
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    Pleistocene aridification cycles shaped the contemporary genetic architecture of southern african baboons
    (Public Library of Science, 2015) Sithaldeen, Riashna; Ackermann, Rebecca Rogers; Bishop, Jacqueline M
    Plio-Pleistocene environmental change influenced the evolutionary history of many animal lineages in Africa, highlighting key roles for both climate and tectonics in the evolution of Africa’s faunal diversity. Here, we explore diversification in the southern African chacma baboon Papio ursinus sensu lato and reveal a dominant role for increasingly arid landscapes during past glacial cycles in shaping contemporary genetic structure. Recent work on baboons ( Papio spp.) supports complex lineage structuring with a dominant pulse of diversification occurring 1-2Ma, and yet the link to palaeoenvironmental change remains largely untested. Phylogeographic reconstruction based on mitochondrial DNA sequence data supports a scenario where chacma baboon populations were likely restricted to refugia during periods of regional cooling and drying through the Late Pleistocene. The two lineages of chacma baboon, ursinus and griseipes , are strongly geographically structured, and demographic reconstruction together with spatial analysis of genetic variation point to possible climate-driven isolating events where baboons may have retreated to more optimum conditions during cooler, drier periods. Our analysis highlights a period of continuous population growth beginning in the Middle to Late Pleistocene in both the ursinus and the PG2 griseipes lineages. All three clades identified in the study then enter a state of declining population size (Ne f ) through to the Holocene; this is particularly marked in the last 20,000 years, most likely coincident with the Last Glacial Maximum. The pattern recovered here conforms to expectations based on the dynamic regional climate trends in southern Africa through the Pleistocene and provides further support for complex patterns of diversification in the region’s biodiversity.
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    Seeing our world through science
    (2013) Sithaldeen, Riashna; Jarrett, Thomas
    We live in a time of exciting discoveries and developments in the field of science, allowing us to 'see' more than ever before, including 'seeing' into the past, the present and the future. For anyone who wants to learn more about seeing our world through science.