Tropical plant knows whose bill is in its flowers

Some plants crave a long bird bill. One tropical plant can even recognize which kind of hummingbird is slurping its nectar by the shape of its bill, scientists report online March 2 in theProceedings of the National Academy of Sciences.

In Heliconia tortuosa, long-billed hummingbirds can reach in and guzzle more nectar than shorter-billed birds, new experiments show, and that prompts the plant to begin reproducing. The plant accepts pollen only from birds with bills that match the shape of its flowers.

The research indicates that “the fine tuning of coevolution between plants and pollinators may be greater than we imagined,” says Ethan Temeles, an ecologist at Amherst College in Massachusetts.

H. tortuosa, an understory plant with slender, red tubelike flowers, is visited by many hummingbird species. Some of the birds have short, straight bills while other species have long, curving bills that echo the flowers’ shape. It seems like the long-billed birds and long-flowered plants evolved to fit each other. Yet “there’s still a lot of debate about how that gets going,” says Matthew Betts, a coauthor of the new study and ecologist at Oregon State University in Corvallis. “How do you end up with these nice tight matches when you’ve got tons of different species visiting the plant?”