Re: light brown apple moth

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At 9:31 AM +1000 4/9/07, Margaret Healey khe36747 wrote:

....In more general terms does anyone know if genetic instability is considered to be greater in pest species of both plants and animals than in other species? Or is just 'out running' their predators their main 'skill' for success?

This interesting article appeared last month, suggesting that for plants, at least, genetic variability drives invasive potential.

http://www.sciencedaily.com/releases/2007/02/070227105553.htm
(article is also available online in the PNAS (http://www.pnas.org/) Early Edition, and will be published March 6, 2007, in the journal's print edition.)


Science Daily - Reed canarygrass is a bit like some people on vacation. At home, they stay on their side of the fence, and speak nicely with the neighbors. But jet them into Las Vegas and by week's end they are shoving other people out of the way in the casino.

Similarly, the reed canarygrass is well-settled in its native European range, not pushing out other species or expanding its terrain. But strains introduced into the United States are running amok ecologically, choking out native plants in wetlands-including in Vermont. Once praised as a fine forage crop, the grass is now considered an invasive pest in at least three states and its range is growing.

Studying this grass as a model, Jane Molofsky, associate professor of plant biology at the University of Vermont and her post-doctoral associate, Sebastien Lavergne, have discovered a novel mechanism to explain the surprising conversion of some plant species from quiet neighbor at home into expansive bully in new territory.

As they report in a forthcoming edition of the Proceedings of the National Academy of Sciences the invasive power of this grass, brought to America in the mid-19th century and many times thereafter comes not from any one individual plant, but from this history of multiple introductions from different regions of Europe.

<snip>

"It's not that you're taking the ones in France and moving them to the US and they're suddenly invasive," Molofsky said, looking over a green swath of reed canarygrass growing in a UVM greenhouse, "its that you move some plants, and then you move some from somewhere else and they recombine here to form something better, genetic superstars."

The result: in America, reed canarygrass has developed traits, like faster emergence in the spring and larger root biomass, that allow it to become a rapid colonizer. In short, the grass is still the same species, but it has quickly evolved to be invasive.

And this has significance far beyond the headache of reed canarygrass. A noteworthy "implication of our paper is that not only do invasive species evolve but we show that they can evolve extremely rapidly," notes Sebastian Lavergne, now at the University of Grenoble in France, striking a blow at the conventional view that evolution occurs at very slow rates.

<snip>

Molofsky's greenhouse- and field-based study, funded by the US Department of Agriculture, shows why. Thanks to a large network of European collaborators, she and her students collected plants from both the center and edge of the native range in Europe, getting individuals from southern France and the Czech Republic. They also collected from the invasive range center in Vermont and the edge in North Carolina.

They discovered that the grass in its native Europe show a typical decrease of genetic diversity at the edge of the range, constraining its ability to adapt and expand into new conditions. But in the US invasive range, they found a different story. There, the invasive plants thrive on infusions of Europe-wide genetic material, allowing them to quickly adapt to new conditions and continue their quiet march into new fields and wetlands.

"The problem is that these invasive species at the range margin are maintaining most of the genetic diversity which represents a substrate for future evolution," Molofsky says, "so when climates begin to change we expect that some individuals from those populations will be able to grow in new conditions. But it is unlikely that native species have maintained enough genetic variability to move with rapid climate changes." Invaders persist, natives expire.

<snip>