05 July 2010

How plants get by when pollinators vanish

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Pity the birds and the bees: disease, climate change and the human urge to pillage our environment mean they are in decline around the world.

So what about the plants that rely on them to spread their seed? A rare "live" study looking at what happens when you deprive plants of pollinators shows that evolution can step in to help them cope. But don't get the champagne out just yet.

Sarah Bodbyl-Roels at the University of Kansas studies the common monkey flower, Mimulus guttatus, a small yellow flower that grows alongside streams in North America. The transition from pollinated to self-pollinating has been recorded in a number of species, she said at the Evolution 2010 conference in Portland, Oregon, this week. "But we haven't seen it in action."

Bodbyl-Roels planted 1600 monkey flower plants in a field and the same number in a greenhouse where they would be isolated from their normal pollinator, the Bombus bumblebee. She then let the plants grow undisturbed for five generations.

Those that had been forced to self-fertilise looked quite distinct from pollinated plants, with smaller flowers in which the female and male organs were much closer together, Bodbyl-Roels told the conference. She says she has identified regions of DNA that are linked to these physical changes.

Crucially, when she looked at how much seed the plants produced – a measure of their ability to reproduce and therefore survive – she found that although seed production in isolated plants crashed for the first three generations, it then increased again. By the fifth generation it was close to the same level as in pollinated plants.

So the good news is that some flowers appear able to recover when their usual pollinators are wiped out, at least in the short term. The study's findings are likely to apply to a large number of other flowering plant species, says Jeffrey Karron of the University of Wisconsin-Milwaukee, and give some hope that the mating systems of flowering plants can evolve to cope with gradual environmental change.

(NewScientist)

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