Study Sheds New Light on Invasive Plant Species

February 03, 2011 - News Release

A group of international scientists, including a University of Guelph biologist, has disproved a commonly held assumption about invasive plant species. The findings appear this week in the journal Ecology Letters.

"Biological invasions are one of the planet's greatest threats to biodiversity and ecosystem services," said U of G integrative biology professor Andrew MacDougall. Invasive plant species present a serious environmental, economic and social problem worldwide, he said.

“However, we are still unable to answer the solution to the so-called 'invasion praradox,' where species that are relatively uncommon can thrive, despite lacking adaptive familiarity with local environmental conditions."

Despite substantial research, scientists know little about why some species dominate new habitats when native plants should technically have the advantage, said MacDougall.

A common but rarely tested assumption is that some special behaviour enables these plants to become more abundant in their new homes than in their native communities. If true, then biosecurity screening procedures should focus on how introduced species behave, he said.

Scientists in a global collaboration called the Nutrient Network, which includes MacDougall's lab, tested this "abundance assumption." They spent three years collecting data for 26 plant species at 39 locations on four continents.

They found that the abundance assumption did not hold for the majority of plant species. Twenty of the 26 species were equally or less abundant at both new and native sites.

"Instead, abundance at native sites can predict abundance at introduced sites, a criterion not currently included in biosecurity screening programs,” said Jennifer Firn of Queensland University of Technology, the study’s lead author. Firn was a visiting scholar in MacDougall's lab in 2008. Thirty-six other scientists were involved in the research.

The Nutrient Network is led by individual researchers at various sites, including MacDougall's site on Vancouver Island. This network is one of only a few collaborations in which individual researchers have run the same experiment at sites around the world.

“Predicting success of invading species is difficult and uncertain but very important," said Henry Gholz, program director in the National Science Foundation’s division of environmental biology, which funds the Nutrient Network.

"The Nutrient Network has enabled a field test of one of the most basic assumptions of current models and found it lacking. The results could lead to better predictions in the future."

Prof. Andrew MacDougall
Department of Integrative Biology
519-824-4120, Ext. 56570/ 53594

For media questions, contact Communications and Public Affairs: Lori Bona Hunt, 519-824-4120, Ext. 53338, or, or Deirdre Healey, Ext. 56982 or

University of Guelph
50 Stone Road East
Guelph, Ontario, N1G 2W1