The world’s biggest flower—which weighs 15 pounds and smells of rotting flesh—evolved from one of the world’s smallest, say the scientists who have finally figured out to which plants Rafflesia is most closely related.
It has been hard to place Rafflesia in a family tree because it is a parasite and lacks many of the characteristics typically used to classify plants. “Its stems, leaves, and roots are dwarfed,” says Charles Davis, the Harvard University evolutionary biologist who collected the flowers in the jungles of Borneo. “It basically has a little threadlike body that winds its way through the host, and you wouldn’t otherwise know it was there except that every now and again it will produce this great big flower.”
Since even the DNA for photosynthesis is missing, Davis and his colleagues turned to mitochondrial and other slowly evolving genes. They pinpointed Rafflesia’s ancestors as flowers with blooms less than one-tenth of an inch across, while Rafflesia blossoms reach three feet in diameter. “It would be like magnifying me to the size of the Great Pyramid of Giza,” Davis says.