Correlates of hyperdiversity in southern African ice plants (Aizoaceae)

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  • Luis M Valente
    Imperial College London Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
  • Adam W Britton
    Imperial College London Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
  • Martyn P Powell
    Imperial College London Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
  • Alexander S T Papadopulos
    Imperial College London Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
  • Priscilla M Burgoyne
    South African National Biodiversity Institute Private Bag X101, Pretoria, 0001, South Africa.
  • Vincent Savolainen
    Imperial College London Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK ; Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3DS, UK.

The exceptionally high plant diversity of the Greater Cape Floristic Region (GCFR) comprises a combination of ancient lineages and young radiations. A previous phylogenetic study of Aizoaceae subfamily Ruschioideae dated the radiation of this clade of > 1500 species in the GCFR to 3.8-8.7 Mya, establishing it as a flagship example of a diversification event triggered by the onset of a summer-arid climate in the region. However, a more recent analysis found an older age for the Ruschioideae lineage (17 Mya), suggesting that the group may in fact have originated much before the aridification of the region 10-15 Mya. Here, we reassess the tempo of radiation of ice plants by using the most complete generic-level phylogenetic tree for Aizoaceae to date, a revised calibration age and a new dating method. Our estimates of the age of the clade are even younger than initially thought (stem age 1.13-6.49 Mya), supporting the hypothesis that the radiation post-dates the establishment of an arid environment in the GCFR and firmly placing the radiation among the fastest in angiosperms (diversification rate of 4.4 species per million years). We also statistically examine environmental and morphological correlates of richness in ice plants and find that diversity is strongly linked with precipitation, temperature, topographic complexity and the evolution of highly succulent leaves and wide-band tracheids.

Keywords

  • Journal Article
Original languageEnglish
Pages (from-to)110-129
Number of pages20
JournalBotanical Journal of the Linnean Society
Volume174
Issue number1
DOIs
Publication statusPublished - Jan 2014
Externally publishedYes
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