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By Stephen Luntz

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Weed Abundance a Myth
Biosecurity authorities base their list of weeds to fear on the belief that invasive species become much more abundant in a new environment than on their home turf. However, an international study has found that this belief is largely a myth.

The lack of animal species adapted to feed on them gives plants an advantage when they invade distant regions of the world, but Dr Jennifer Firn of Queensland University of Technology found that this doesn’t usually translate to higher densities of the introduced plant.

Firn and her colleagues did not set out to study introduced plants. They are part of a global collaboration called the Nutrient Network, which is comparing the biological productivity of similar sites around the world.

Firn believes that because they were looking for something else gave the Nutrient Network an advantage when studying the behaviour of introduced species. “If you’re studying an invasive species you look in the places they’re known to be common,” she says. This gives an exaggerated indication of their abundance. The Nutrient Network, on the other hand, was using sites that were effectively random.

Firn says there are exceptions to the pattern of plants being found at similar frequencies to their native territory, such as several species of the grass Alopecurus, but most follow the...

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