a1 Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, IL 60022, USA.
a2 Northwestern University, Plant Biology and Conservation, 2205 Tech Drive, Evanston, IL 60208, USA.
a3 Current address: University of California, Berkeley, Department of Integrative Biology, 3060 Valley Life Sciences Building #3140, Berkeley, CA 94720, USA. E-mail: [email protected]
Dorstenia, the second largest genus (105 species) within the Moraceae, is the only genus in the family with woody, herbaceous and succulent species. All but one species of Dorstenia are restricted to the Neotropics or Africa, and it is the only genus in the family with an almost equal transatlantic distribution. This work presents the first molecular phylogeny and the first evolutionary study to examine origin and diversification within the genus. We inferred the phylogeny with ITS sequence data using Bayesian and maximum likelihood approaches. We tracked the evolution of distinct morphological characters and tested for correlated evolution in multiple characters. Time and place of Dorstenia’s origin were estimated to test a post-Gondwanan versus a Gondwanan origin hypothesis using fossil calibrations, Bayesian molecular dating, and maximum likelihood-based ancestral range reconstructions. Our phylogenetic analysis supports the monophyly of Dorstenia; previous subgeneric classifications are polyphyletic and must be re-evaluated. Woody habit, phanerophytic life form, macrospermy, and lack of storage organs are ancestral traits found in African Dorstenia. Evolution of woodiness and macrospermy are correlated. Dorstenia appears to have originated in Africa, radiated into the Neotropics and subsequently re-colonised Africa. Whether or not the extant distribution is the result of vicariance or dispersal is equivocal.
(Received November 19 2011)
(Accepted July 05 2012)