Evolution and Diversification in the Sapindales
Weeks, Andrea .
Historical biogeography of endemic Namibian Commiphora (Burseraceae): evolution in a steady-state landscape?
Emerging paleontological and molecular systematic data suggest that Miocene-age aridification in Africa had a profound effect on the evolution of resident plant and animal groups by expanding arid habitat or by imposing biogeographic barriers. Such a scenario may explain the radiation of a subset of African species in the myrrh genus Commiphora (Burseraceae; 190 spp.) that has a crown group age of 27.8 Â± 4.5 My. Approximately 150 Commiphora spp. are distributed among the continent’s (sub-)tropical seasonally dry biomes and are most diverse in North East and Tropical East Africa. Finer-scale geological studies of these and other areas reveal dynamic fluctuations in temperature, precipitation and vegetation types before, during and after the Miocene. This evidence suggests the causal factors in Commiphora’s diversification may have been considerably more complicated, particularly during the ca. 20 My interval between Commiphora’s stem (53.6 - 47.2 Mya) and crown group radiation. The Namib Desert is an exceptional biogeographic region: since the Early Cretaceous, this landform has been largely immune to the geomorphological, climate and vegetation changes recorded elsewhere in the continent. Eighteen Commiphora species are endemic to Namibia or extreme northwest South Africa, and 14 are limited to the Namib Desert or the adjacent Escarpment. Estimates for the age of the Namib (130 - 80 My) predate the evolution of Commiphora. Given its documented long-term ecological stability, the Namib may retain members of basal Commiphora lineages that gave rise to more recent East African clades. This presentation reports the results from the test of this hypothesis using molecular phylogenetic analysis of all Namibian species and those with more widespread distribution in Africa. Comparative DNA sequence data from the nuclear ETS and chloroplast psbA–trnH region are presented.
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1 - George Mason University, Department of Environmental Science and Policy 5F2, Fairfax, Virginia, 22030, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Boulevard B/Hilton
Date: Tuesday, July 10th, 2007
Time: 10:45 AM