The Evolution of the Orchid and the Orchid Bee
Sarah Zielinski
Smithsonian.com
September 23, 2011

When scientists delve into studies of the co-evolution
of plants and their pollinators, they have something of
a chicken/egg problem-which evolved first, the plant or
its pollinator? Orchids and orchid bees are a classic
example of this relationship. The flowers depend on the
bees to pollinate them so they can reproduce and, in
return, the bees get fragrance compounds they use during
courtship displays (rather like cologne to attract the
lady bees). And researchers had thought that they co-
evolved, each species changing a bit, back and forth,
over time.

But a new study in Science has found that the
relationship isn't as equal as had been thought. The
biologists reconstructed the complex evolutionary
history of the plants and their pollinators, figuring
out which bees pollinated which orchid species and
analyzing the compounds collected by the bees. It seems
that the orchids need the bees more than the bees need
the flowers-the compounds produced by the orchids are
only about 10 percent of the compounds collected by the
bees. The bees collect far more of their "cologne" from
other sources, such as tree resin, fungi and leaves.

And it was the bees that evolved first, the researchers
found, at least 12 million years before the orchids.
"The bees evolved much earlier and independently, which
the orchids appear to have been catching up," says the
study's lead author, Santiago Ramirez, a post-doc at the
University of California at Berkeley. And as the bees
evolve new preferences for these chemical compounds, the
orchids follow, evolving new compounds to lure back
their bee pollinators.

But this study is more than just an interesting look
into the evolution of two groups of organisms. The
researchers note that in the context of the current
decline of bee populations worldwide, their research has
disturbing implications for what that decline might mean
for plants. "Many of these orchids don't produce any
other type of reward, such as nectar, that would attract
other species of bee pollinators," Ramirez notes. "If
you lose one species of bee, you could lose three to
four species of orchids."

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