Relatives Found for the World's Stinkiest Flower

The relatives of the largest and smelliest flower in the world, Rafflesia, have finally been found. This family, the Euphorbiaceae -- known for some of the smallest flowers in the world, too -- includes the poinsettia, Irish bells, the rubber tree, and castor oil plant.

The plant is found on the Indonesian island, Sumatra. It is a parasite that steals nutrients from another plant while deceiving insects into pollinating it. Its blood-red flowers can weigh as much as 7 kilograms (15 pounds ) and they smell like decaying flesh. And they even can emit heat, possibly mimicking a newly killed animal to tempt the carrion flies that pollinate it.

"They really do look and smell like rotting flesh. They are a totally fetid, stinking, foul kind of flower. It can be totally repulsive to so many of us. But to the flies that visit these things, it's just delightful," said Harvard University plant biologist Charles Davis, who led the research.

Plant lineages have been based on genes related to photosynthesis, but that was not possible with rafflesia. The researchers had to look to other parts of its genome for molecular clues to identify its evolutionary relationships.

According to the molecular data, Rafflesia are ancient plants, dating back to the Cretaceous Period, 100 million years ago, when dinosaurs still roamed the earth and flowering plants were first making an appearance. The researchers discovered that over a span of 46 million years, Rafflesia's flowers evolved a 79-fold increase in size before assuming a slower evolutionary pace.

"These plants are so bizarre that no matter where you put them with any group of plants, you're going to have a lot of explaining to do," Davis said. "But what was surprising was that with all of the options available as close relatives, they are nested within this group of plants with absolutely tiny flowers."

This research was published in the top-tier journal, Science.

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