Historical biogeography of Androcymbium Willd. (Colchicaceae) in Africa: evidence from cpDNA RFLPs

Authors

  • JULI CAUJAPÉ-CASTELLS,

    1. Section of Integrative Biology and Institute of Cellular and Molecular Biology, University of Texas, Austin, Texas 78713-7640, USA
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    • *Juli Caujapé-Cas-tells, Jardín Botánico Canario ‘Viera y Clavijo’ Apartado 14 de Tafira Alta, 35017 Las Palmas de Gran Canaria, Spain. E-mail: julicaujape@granca.step.es

  • ROBERT K. JANSEN,

    1. Section of Integrative Biology and Institute of Cellular and Molecular Biology, University of Texas, Austin, Texas 78713-7640, USA
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  • NÚRIA MEMBRIVES,

    1. Estació Internacional de Biología Mediterrania-Jardí Botànic Marimurtra, Psg. Karl Faust 10, 17300 Blanes, Girona (Spain)
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  • JOAN PEDROLA-MONFORT,

    1. Estació Internacional de Biología Mediterrania-Jardí Botànic Marimurtra, Psg. Karl Faust 10, 17300 Blanes, Girona (Spain)
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  • JOSEP M. MONTSERRAT,

    1. Institut Botanic de Barcelona, Avinguda Muntanyans s/n, Pare de Montjuic. 08038 Barcelona (Spain)
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  • AMPARO ARDANUY

    1. Estació Internacional de Biología Mediterrania-Jardí Botànic Marimurtra, Psg. Karl Faust 10, 17300 Blanes, Girona (Spain)
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Abstract

The cpDNA restriction variation in 39 populations representing a geographical sampling of 18 species of Androcymbium in southwestern and northern Africa was examined to assess the historical biogeography of the genus. The cpDNA phylogeny indicates that the disjunction between South and North Africa is best explained by the dispersal of southern African ancestors into North Africa. Divergence time estimates suggest that the geographic range of the genus may have extended considerably north (perhaps to Tanzania and Kenya) prior to the global desiccation of Africa in the Miocene. Further expansion of the genus northward was probably stalled until climatic changes in the late Miocene brought about the gradual replacement of a subtropical woodland savanna with the arid landscape that gave rise to the Sahara. Aridification of the northern quarter of the continent provided the ecological conditions for fostering the expansion of Androcymbium along the Mediterranean fringe (probably east to west) and its introduction into the Canary Islands. Unlike their South African congeners, the northern species have experienced expansions, fragmentations, and local extinctions in response to the severe climatic shifts in this area during the Pliocene-Pleistocene. According to our divergence time estimates, the arid track may have already existed as a continuous area connecting southern and northern Africa in the late Miocene.

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