Misiewicz, Tracy , Zerega, Nyree J C .
Illuminating the Evolutionary History of Dorstenia (Moraceae): Investigating the Gondwanan Hypothesis.
With 105 species, Dorstenia is the second largest genus within the Moraceae (Mulberry) family (~1100 species), second only to Ficus (~750 species), and the only member of the family with woody, herbaceous and succulent species. With one exception, all Dorstenia species are restricted to the Neotropics and Africa. Dorstenia is also the only genus in the Moraceae family with an almost equal distribution of species on either side of the Atlantic Ocean. This distribution has lead to the hypothesis that Dorstenia originated before Africa and South America split apart from Gondwana 105 million years ago and Dorstenia species on each continent subsequently underwent separate radiations. Alternatively, Dorstenia could have originated post-Gondwana and dispersed or migrated from one continent to the other. Presented here is the first phylogenetic reconstruction of Dorstenia. Using ITS sequence data we tested biogeographical hypotheses and traced the evolution of specific morphological characters, such as woody and succulent habits, which are thought to be primitive and found only in Old World species, to herbaceousness which is found in both New and Old World species. Molecular dating using fossil data and penalized likelihood was been used to date divergence times within the genus and to explore hypotheses for possible dispersal routes and mechanisms. Our preliminary results show that the genus diverged well after the split of Africa from South America and migrations between the two continents are proposed via the North Atlantic Land Bridge during the Eocene.
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1 - Northwestern University, Plant Biology and Conservation, 633 Clark Street, Evanston, Il, 60208, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 11:00 AM