That darn orchid !!!


Plants rely on insects and wind to disperse their pollen. In order to attract insects, plants have bright colors and sweet scents that promise a food reward such as nectar. But are all plants so kind as to reward their pollinators? The Australian orchid, Chiloglottis trapeziforms , is one of the exceptions to this type of behavior. These plants attract pollinators purely by deception. This orchid's appearance is remarkably similar to that of a female wasp. Not only is the appearance of the Australian orchid deceiving, it also tricks male wasps by producing a floral odor that mimicks a single female horomone, also known as a pheromone. The orchid wasp is fooled into thinking that a lovely female is waiting to mate. The wasp then engages in a behavior known as pseudocopulation. At this time pollination is achieved. What a surprise for the wasp!! He leaves dumbfounded and in search of another mate, but little does he know he has been used only to make re! production successful for another species. If the wasp is smart he will not be tricked by another orchid, but some aren't so bright. When deceived again by another orchid the wasp will land and fertilize this orchid.

This behavior is an example of coevolution. The orchid is very specific in terms of choosing pollinators so they must be able to adapt to the changes that occur in the wasps. After being deceived a few times the "smart" wasps will learn to avoid orchid patches. Also, mutations may occur that help the wasps better distinguish between the orchid odor and the female pheromone giving them an advantage over their counterparts. Since the wasps are evolving to learn how to avoid the orchid's trickery the orchid must also adapt. At one time the orchids produced a flowery aroma, but in order to benefit from sexual deception the flower must continually develop an odor that is harder to tell apart from the wasp pheromones.