Orchid bees than in the evolution
Orchid bees are not so dependent on orchids, after all, a new study that challenges the prevailing view of how plants and their pollinators evolve together.
A long-standing belief among biologists consider the species in the highly specialized relations to engage in constant back-and-forth play of co-evolution.
“We found that this reciprocal specialization does not exist for orchid bees and orchids,” said study lead author Santiago Ramirez, a postdoctoral researcher in the laboratory of Neil Tsutsui, Associate Professor at the University of California, Berkeley Department of Environmental Science, Policy and Management. “Bees have evolved much earlier and independently, while orchids seem to have been catching up.”
The connection between bees and plants specific, they visited the orchid has been well documented by botanists and naturalists, including Charles Darwin. Biologists have discovered that male bees necessary, specific aroma compounds produced by flowering plants in order to mate with female bees.
In the study, published in the September 23 of the journal Science, the researchers tested more than 7,000 individuals and male bees sequenced DNA from 140 pollinaria orchids, which are small packets that contain all the pollen grains produced by a single flower. The researchers were able to infer the evolutionary history of both bees and orchids, and to establish which species of bee pollinates what species of orchids. The researchers also quantified and analyzed scents collected by bees to orchid and compared with the compounds produced by the orchid flowers.
Male orchid bees can find the fragrance compounds needed for mating from decaying logs, as shown here, and orchids. (B. Jacobi photo)
To their surprise, scientists found that bees have evolved at least 12 million years earlier than their counterparts in orchids. In addition, they found that the compounds produced by orchids accounted for 10 percent of the compounds collected by their pollinators. The remaining 90 percent could come from other sources, including tree resins.
“It seems that male bees developed a preference for collecting these compounds in a variety of sources, and orchids have converged on the preference for millions of years before chemicals,” said Ramirez.
In essence, orchids need their bee pollinators than bees need.
The results have implications for conservation biology, partly because of the alarming decline over the last 15 years of pollinating bees in the world.
“Many plant species are highly dependent on their pollinators,” said Ramirez, who began this work while he was a Ph.D. student in the laboratory of Naomi Pierce, Harvard University biology professor. “If you lose a species of bee, you could lose three to four species of orchids. Many of these orchids do not produce any other type of reward such as nectar, which may attract other species of pollinating bees. ”
“Our study is consistent with the emerging theory that insect sensory biases have played a major role in the conduct of reproductive adaptations of flowering plants,” said Ramirez. “It highlights the ecological and evolutionary interdependence of flowering plants and their pollinators specialist, suggesting that new threats to pollinators can have profound effects on the ecosystems they inhabit.”