Climate-driven rampant speciation of the Cape flora

Authors

  • Lydie M. Dupont,

    Corresponding author
    1. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str, DE-28359 Bremen, Germany
      Lydie Dupont, MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str, DE-28359 Bremen, Germany.
      E-mail: dupont@uni-bremen.de
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  • Hans Peter Linder,

    1. Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, CH 8008 Zurich, Switzerland
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  • Florian Rommerskirchen,

    1. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str, DE-28359 Bremen, Germany
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  • Enno Schefuß

    1. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str, DE-28359 Bremen, Germany
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Lydie Dupont, MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str, DE-28359 Bremen, Germany.
E-mail: dupont@uni-bremen.de

Abstract

Aim  To test whether the radiation of the extremely rich Cape flora is correlated with marine-driven climate change.

Location  Middle to Late Miocene in the south-east Atlantic and the Benguela Upwelling System (BUS) off the west coast of South Africa.

Methods  We studied the palynology of the thoroughly dated Middle to Late Miocene sediments of Ocean Drilling Program (ODP) Site 1085 retrieved from the Atlantic off the mouth of the Orange River. Both marine upwelling and terrestrial input are recorded at this site, which allows a direct correlation between changes in the terrestrial flora and the marine BUS in the south-east Atlantic.

Results  Pollen types from plants of tropical affinity disappeared, and those from the Cape flora gradually increased, between 10 and 6 Ma. Our data corroborate the inferred dating of the diversification in Aizoaceae c. 8 Ma.

Main conclusions  Inferred vegetation changes for the Late Miocene south-western African coast are the disappearance of Podocarpus-dominated Afromontane forests, and a change in the vegetation of the coastal plain from tropical grassland and thicket to semi-arid succulent vegetation. These changes are indicative of an increased summer drought, and are in step with the development of the southern BUS. They pre-date the Pliocene uplift of the East African escarpment, suggesting that this did not play a role in stimulating vegetation change. Some Fynbos elements were present throughout the recorded period (from 11 Ma), suggesting that at least some elements of this vegetation were already in place during the onset of the BUS. This is consistent with a marine-driven climate change in south-western Africa triggering substantial radiation in the terrestrial flora, especially in the Aizoaceae.

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