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Warming Could Spur 'Evolution Explosion'

January 09, 2007 — By Deborah Zabarenko, Reuters 



WASHINGTON -- Fast-growing weeds have evolved over a few generations to adapt 
to
climate change, which could signal the start of an "evolution explosion" in
response to global warming, scientists reported Monday. 

This means that the weeds will likely keep up with any attempts to develop 
crops
that can adapt to global warming, said Arthur Weis, a professor of ecology and
evolutionary biology at the University of California, Irvine. 

But some long-lived species -- like the venerated California redwood tree, 
with a
life-span of hundreds of years -- will not have the capacity to adapt so 
quickly,
because their life cycles are so long, Weis said in a telephone interview. 

The quick-growing weedy plant known as field mustard showed the ability to 
change
reproductive patterns over a period of just seven years, Weis said. 

"If you take a climate shift, such as we've had here in southern California, 
in a
very few number of generations you can get a change in ecologically important
traits that can allow these fast-growing weedy species to hang on and 
actually do
well despite the change in environments," he said. 

Weis and his colleagues cultivated two sets of mustard seeds in a greenhouse: 
one
set collected in 1997, just before a five-year drought, and a second set
collected in 2004, after the drought ended. 

The plants were divided into three groups, with each getting different 
amounts of
water, ranging from drought-dry to soggy. In every case, the post-drought
generation of plants flowered earlier, meaning the plants could produce seeds
before the soil dried out. Late-bloomers would wither before any seeds were
produced in a drought year. 

SPEEDED-UP LIFE-CYCLE 

How fast a change is this, on the evolutionary timetable? Weis calculated that
this represents a 16 percent acceleration of the mustard plants' life-cycle 
over
seven generations. 

"That's a pretty big change in age of maturation," he said. 

Asked to hypothetically compare this to evolutionary changes in people, Weis
offered what he termed a very crude analogy: if humans evolved at the same 
rate
as the mustard plants in the experiment, the average onset of the age of
reproduction in humans would slip from 16 years to 13 1/2 in seven 
generations. 

Weis is spearheading a project to collect, dry and freeze seeds from around 
North
America so they can be studied 50 years from now. He figures that global 
warming
will prompt lots of evolutionary changes and scientists will want to have
evidence of plants before the changes occurred. The effort is called Project
Baseline. 

"If global climate change is coming, and it is, we have this huge unplanned
experiment in evolutionary biology facing us," Weis said. "Climate change 
could
lead to an evolution explosion. ... This gives scientists an unprecedented
opportunity to look at the actual nuts and bolts of evolutionary change." 

The idea is for scientists in the mid-21st century to go back to the same
locations where plants are being collected and note the differences between 
the
plants from the different time periods. 

Research by Weis and his team was published in the journal Proceedings of the
National Academy of Sciences.

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