Browsing by Author "Hoffmann, Vera"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Open Access
    Dated Plant Phylogenies Resolve Neogene Climate and Landscape Evolution in the Cape Floristic Region
    (Public Library of Science, 2015) Hoffmann, Vera; Verboom, G. Anthony; Cotterill, Fenton P. D.
    In the context of molecularly-dated phylogenies, inferences informed by ancestral habitat reconstruction can yield valuable insights into the origins of biomes, palaeoenvironments and landforms. In this paper, we use dated phylogenies of 12 plant clades from the Cape Floristic Region (CFR) in southern Africa to test hypotheses of Neogene climatic and geomorphic evolution. Our combined dataset for the CFR strengthens and refines previous palaeoenvironmental reconstructions based on a sparse, mostly offshore fossil record. Our reconstructions show remarkable consistency across all 12 clades with regard to both the types of environments identified as ancestral, and the timing of shifts to alternative conditions. They reveal that Early Miocene land surfaces of the CFR were wetter than at present and were dominated by quartzitic substrata. These conditions continue to characterize the higher-elevation settings of the Cape Fold Belt, where they have fostered the persistence of ancient fynbos lineages. The Middle Miocene (13-17 Ma) saw the development of perennial to weakly-seasonal arid conditions, with the strongly seasonal rainfall regime of the west coast arising ~6.5-8 Ma. Although the Late Miocene may have seen some exposure of the underlying shale substrata, the present-day substrate diversity of the CFR lowlands was shaped by Pliocene-Pleistocene events. Particularly important was renewed erosion, following the post-African II uplift episode, and the reworking of sediments on the coastal platform as a consequence of marine transgressions and tectonic uplift. These changes facilitated adaptive radiations in some, but not all, lineages studied.
  • Thumbnail Image
    Item
    Open Access
    Plants as biotic indicators of Neogene palaeoenvironmental evolution in the Cape Floristic Region
    (2012) Hoffmann, Vera; Verboom, George Anthony; Cotterill, FPD
    Comparative biologists have refined the synthesis of molecularly dated phylogenies and ecological data into an important tool to reconstruct the evolution of species and biomes, and to unravel the history and role of abiotic determinants of diversity patterns (fire, climate, tectonism). This has been extended into the cross-disciplinary, geobiological approach of 'geoecodynamics' has exploits the spatial fidelity of locally restricted organisms to unravel the temporal and spatial evolution of landforms. This research approach is adopted here across 11 plant clades representing six prominent plant families of the Cape flora (Asteraceae, Orchidaceae, Restionaceae, Cyperaceae, Poaceae and Proteaceae) to infer (i) the relative roles of climatic changes and neotectonic uplift in shaping the CFR since the Early Miocene, and to detemine (ii) whether contrasting evolutionary processes (adaptive versus non-adaptive) exhibit spatial structuring within the flora, given the complex topography of the region.