"researchers have determined one orchid is so attractive to male bees that the males actually prefer sex with the orchid over sex with female bees of their own species. ... Ophrys orchids -- can compete with female insects for male attention.
... three powerful "weapons" that overwhelm male Colletes cunicularius bees through sight, touch and smell. All three mimic characteristics of female bees that are ready to mate. "The visual mimicry includes (copying) the color and shape of a female (bee)," co-author Florian Schiestl told... "Tactile memory includes (copying) the hairs on the body of a female," added Schiestl, a University of Zurich botanist and biologist. He and colleague Nicolas Vereecken focused, however, on the orchid's perfume, which humans cannot smell, but is irresistible to male bees. One whiff of the scent encourages the bees to hop on flowers and mate with them, just as they would with a female bee. Unbeknownst to the male, pollen from the flower attaches to the bee during the process, so that when he hops to another flower, pollination takes place. For the study, published in... Proceedings of the National Academy of Sciences, the scientists collected 391 virgin C. cunicularius female bees and multiple Ophrys flowers from 15 different populations across Western Europe. Most females within solitary bee species mate just once during their lifetime, so finding virgins wasn't too difficult. The scientists analyzed the chemical composition of sex pheromones emitted by the female bees and compared this to the chemical make-up of the orchid's perfume. The mixtures were nearly the same, containing the same compounds, except the chemical ratios were different in the orchid, meaning that the flower's perfume wound up being its own unique blend, which the male bees actually preferred over the scent of the female bees' sex pheromones. The researchers tested this fact by tweaking the female pheromones so that they matched the orchid's perfume. The scent, as expected, drove male bees into a lovemaking frenzy. Schiestl explained that male bees are attracted to novelty, which helps to avoid inbreeding, so imperfect mimicry by the orchid benefits the flower more than if it were to exactly copy the smell of a female bee. He said his own prior research shows "that the mimicking of females (by orchids) comes from pre-adaptations that are evolutionarily older than the actual female mimicry." For that earlier work, he and his colleagues found that the orchid was already making chemicals similar to those produced by female bees before the insect seduction took place, so the flower was in a good position to take advantage of the situation. Santiago Ramirez, a researcher in Harvard University's Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, recently determined all orchids arose between 76 to 84 million years ago, when dinosaurs were still roaming the planet. The evidence discovered by Ramirez and his team consisted of the remains of an ancient orchid pollen-bearing bee... Scientific interest in the orchid/bee relationship is, by default, much more recent, but goes back many decades. "Since the time of Darwin, evolutionary biologists have been fascinated with orchids' spectacular adaptations for insect pollination," Ramirez said, adding that he's particularly interested in Vanilla orchids, as the fragrant and tasty genus Vanilla represents one of the oldest known groups within the orchid plant family." URL : http://dsc.discovery.com/news/2008/05/27/bee-orchid-sex.html ********************* Regards, VB _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
