How Deceptive Can an Orchid Be?
Aug. 12, 2009 — -- Charles Darwin would have loved it.
Scientists have found that an orchid on the Chinese island of Hainan is even trickier than most orchids, admired by the great naturalist for their cleaver abilities to deceive pollinators.
Unlike many other orchids, the Dendrobium sinense doesn't produce an aroma that will lure bees into its boudoir, probably because bees don't serve as its pollinators.
The white orchid depends on the hornet Vespa bicolor to spread its pollen, but it has developed a self-serving technique to get the hornet to do it. The orchid releases a chemical that produces an aroma that is identical to the smell made by bees that are under attack.
The hornet normally captures bees to feed to its larvae, so when it smells the alarm pheromone it figures bees are inside the orchid, and they are in distress and thus would be easy victims. So the hornet plunges into the orchid like a cruise missile.
But there are no bees there. Only pollen, which clings to the body of the hornet. The hornet moves on, getting nothing for its efforts, and it spreads the pollen to other orchids in the Bawangling National Nature Reserve in Hainan.
Scientists in China and at the University of Ulm in Germany spent 121 hours studying the orchid, watching hornets as they "pounced on the red center of the flower, much like their behavior when attacking prey," according to their study, published in Current Biology.
That may be among the most insidious routines in the enormous family of orchids, which numbers between 20,000 and 30,000 species and is the largest and most diverse plant family on Earth. Orchids flourish all over the planet, from north of the Arctic Circle to an island off Antarctica, which is why they fascinated Darwin.
Darwin turned to orchids for evidence to support his theory of natural selection. How had they adapted to virtually every climate on the Earth?
Orchids come in nearly all sizes, in all shapes and in all colors except black. Most of them cling to trees, escaping from a jungle floor that has so many aggressive plants that they would likely have been crowded out. So they live on air instead of soil, thriving under conditions that would be impossible for nearly all other plants.
