Floral Gigantism in Rafflesiaceae

doi:10.1126/science.1135260

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Published Online January 11, 2007
Science DOI: 10.1126/science.1135260

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Submitted on September 18, 2006
Accepted on December 26, 2006

Floral Gigantism in Rafflesiaceae

Charles C. Davis ¹^*, Maribeth Latvis ¹, Daniel L. Nickrent ², Kenneth J. Wurdack ³, David A. Baum ⁴

¹ Department of Organismic and Evolutionary Biology, Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA 02138, USA.
² Department of Plant Biology, Southern Illinois University, 1125 Lincoln Drive Carbondale, IL 62901-6509, USA.
³ Department of Botany Smithsonian Institution, NMNH MRC-166 Washington, DC 20013-7012, USA.
⁴ Department of Botany University of Wisconsin, 430 Lincoln Drive Madison, WI 53706, USA.

^* To whom correspondence should be addressed.
Charles C. Davis , E-mail: cdavis{at}oeb.harvard.edu

Species of Rafflesiaceae possess the world's largest flowers(up to 1 m in diameter), yet their precise evolutionary relationshipshave been elusive, hindering our understanding of the evolutionof their extraordinary reproductive morphology. We present resultsof phylogenetic analyses of mitochondrial, nuclear, and plastiddata showing that Rafflesiaceae are derived from within Euphorbiaceae,the spurge family. Most euphorbs produce minute flowers, suggestingthat the enormous flowers of Rafflesiaceae evolved from ancestorswith tiny flowers. Given the inferred phylogeny, we estimatethat there was a ca. 73-fold increase in flower diameter onthe stem lineage of Rafflesiaceae, making this one of the mostdramatic cases of size evolution reported for eukaryotes.