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 on
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.
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.
