Family ties. The land-based Venus flytrap (top) is close kin to the aquatic waterwheel (bottom).

Carnivorous Plant Siblings Reunited

Like siblings, closely related plants can sometimes have very different lifestyles. That proves to be true of two carnivorous plants that live on opposite sides of the Atlantic and in completely different habitats. Despite these differences, new DNA studies show that the Venus flytrap and another plant called the waterwheel are each other's closest kin, a result that rearranges the family tree for carnivorous plants.

Carnivorous plants have come up with a variety of ways to snare their prey: pools of water for drowning unlucky visitors, sticky surfaces that work like flypaper, or “snap traps” that clamp down on morsels in a matter of milliseconds. Waterwheels and Venus flytraps depend on snap traps. Charles Darwin thought the two were closely related. But a century later, researchers looking closely at the morphology of these plants decided that the waterwheel's closest kin was not the Venus flytrap but the terrestrial sundew, which dines on insects caught with its flypaper trap.

Darwin's hunch was right after all, says Kenneth Cameron of the New York Botanical Garden. He and his colleagues compared the DNA from four genes of about a dozen carnivorous plants. They conclude that the world's only two snap-trapping plants really are sibling species, whereas the sundew is no closer than a cousin, sharing a more distant common ancestor, the group reports in the September issue of the American Journal of Botany.

In many ways, this revised family history makes sense, comments Mark Chase, a plant systematist at the Kew Royal Botanical Gardens in Surrey, U.K.--even though he once suggested otherwise. And now that this close relationship is “nailed down, it sets the stage for people to ask more intelligent questions about how these mechanisms evolved,” Chase points out.

Related sites
History and evolution of carnivorous plants, plus growing tips
International Carnivorous Plant Society