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Abstract Detail


Systematics Section

Berry, Paul E. [1], Van Ee, Benjamin [2], Riina, Ricarda [3], Haber, Elizabeth [1].

The radiation of Croton (Euphorbiaceae) on Madagascar - how did this group become so speciose and diversified there compared to other Old World areas?

Prior to the use of molecular data, Croton (Euphorbiaceae) was thought to have originated in the Old World. Although the African, Asian, and Australian species of Croton span much of the range of morphological variation within the genus, DNA sequence data to date indicate that they form a single clade derived from a New World ancestor. Of the estimated 400 Old World species of Croton, about 150 of them are endemic to Madagascar, and the species there vary from microphyllous subshrubs to tall trees, with a number of unusual vegetative and floral features for the genus, such as numerous species with opposite or whorled leaves, and species groups with much enlarged pistillate calyces. It is also one of the three most speciose genera on the island. We have begun field studies of Croton in Madagascar, with over 50 of the 150 species sampled to date. Molecular studies are underway to determine if the Malagasy species represent a single evolutionary radiation, or if there are a number of distinct lineages possibly derived from different African ancestors. Despite a remarkable morphological convergence of some of the tree species from Madagascar with the South American dragonís blood group, they are not closely related at all. This study will result in a taxonomic revision of Croton in Madagascar and an update for the online version of the Catalogue of the Vascular Plants of Madagascar.


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Related Links:
Croton Research Network
Harvard University Herbaria
University of Michigan Herbarium


1 - University of Michigan, Herbarium & Dept. Ecology and Evolutionary Biology, 3600 Varisty Drive, Ann Arbor, MI, 48108, USA
2 - Harvard University, Arnold Arboretum, Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA, 02138, USA
3 - University of Michigan, Herbarium and Dept. of Ecology and Evolutionary Biology, 3600 Varsity Dr., Ann Arbor, MI, 48108, USA

Keywords:
Croton
Euphorbiaceae
megadiverse
Madagascar
molecular phylogenetics
Biogeography
Africa
Asia
Australia.

Presentation Type: Oral Paper:Papers for BSA Sections
Session: 57
Location: Maybird/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 9:30 AM
Number: 57007
Abstract ID:816


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