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Mimicry: The Orchid and the Bee

This photograph, from The Sex Life of Flowers by Meeuse and Morris, is an example of mimicry in which the orchid has evolved to resemble a female bee. The male, trying unsuccessfully to mate with the flower, unwittingly collects and spreads the orchid's pollen.

Credits: Courtesy of Oxford Scientific Films

Mimicry: The Orchid and the Bee

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Resource Type:
Image

Format:
Graphic

Topics Covered:
Adaptation and Natural Selection

Backgrounder

Mimicry: The Orchid and the Bee:

Some people -- and animals -- will go to any lengths to attract members of the opposite sex, including the use of aliases and lies. As many as 10,000 species of dainty orchids in the floral world also utilize deception in order to be get pollinated: Over time, they have evolved elaborate ruses to lure insects.

Generally we think of flowers as offering food to the insects that pollinate them. Evolution has produced many flower species that pretend to have food that insects want, emitting scents of coconut or even rotting meat. Some orchids, however, appear to offer the promise of sex: They have evolved to resemble female versions of certain insects.

The pseudo-copulation strategy of the orchid enables it to spread its genes widely. The mimicry is near-perfect. For example, the Australian hammer orchid has taken advantage of a mating ritual of the Thynnid wasp, which involves a female wasp waiting on top of a branch or plant for a male to spot her. The hammer orchid's flower mimics the female wasp looking upward for a male flying by, complete with a fake shiny head and furry body. The orchid even releases an enticing female wasp pheromone.

When the male wasp tries to mate with the dummy female, he fails, but the orchid succeeds in getting pollen on the wasp. He flies away, only to be fooled again by another orchid pulling the same trick. In the process, the wasp transfers pollen from flower to flower.

Place a real female wasp next to the orchid mimic, and a male wasp will spot the real deal. For this reason, natural selection has favored flowers that happen to bloom in the period when male wasps are flying but females are not out yet.

Why orchids have evolved sexual mimicry for pollination is open for debate. Plants that are farther away from each other are more likely to be distant relatives, so mimicry may reduce inbreeding. Posing as a sexual suitor may be a strategy that allows the geographic spread of plants over a wide area -- generally, insects will travel further to find a mate than to find a meal. To test these hypotheses, scientists are studying both the mating behavior of the insect pollinators and the growth and reproduction of the deceptive orchids.

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