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ScienceShot: Copycat Orchids

The turtle shell orchid is a dainty yellow beauty—and also an identity thief, according to a new study. The flower (Rossioglossum ampliatum, above right) is a member of the Oncidiinae group of orchids in the tropical Americas. Most don't make nectar, so they lure pollinators by trickery. To expose the orchids' scam, researchers examined dozens of Oncidiinae orchids growing in Costa Rica and elsewhere. They found that roughly 500 are an unusual color called bee-UV-green, visible to bees but not humans. That's the same color as several flowers from the Malpighiaceae family, which offer bees a reward of oil that they can eat or use for nest-building and grow in many of the same places as Oncidiinae orchids. All the bee-UV-green orchids also copy the shape of these oily flowers. The image shows a blossom, center, from a Malpighiaceae species of liana (Stigmaphyllon lindenianum) and, on the left, an Oncidiinae orchid (Trichocentrum ascendens); both look bee-UV-green to bees. To determine whether it's just a coincidence that T. ascendens is identical in color to Malpighiaceae species, the researchers randomly chose pairs of Costa Rican flowers and compared their colors. Members of each random pair weren't at all alike in color, suggesting that the similarity between the oily flower and its orchid doppelganger is greater than would be expected by chance. Fourteen different branches of the Oncidiinae family tree independently evolved into mimics of oily flowers, the team reports online today in the Proceedings of the Royal Society B, suggesting that even for orchids, crime does pay.

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