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Phylogenetic Relationships of Invasive Plants Are Useful Criteria for Weed Risk Assessments

Tuesday, November 7, 2023
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Human activity has introduced plant and animal species to completely new areas around the globe. Some of these newcomers become invasive species that spread and cause harm to the environment. It is difficult to control invasive species once they have arrived, so one of the best ways to minimize their harm is to prevent their introduction in the first place.

Weed risk assessments are tools used to regulate imported plants and evaluate whether a new species could become invasive. They typically include questions about the biology and ecology of the species of interest, but the content of these questionnaires varies significantly depending on which governments or agencies administer them, and they have a mixed track record for catching new invaders. A new study authored by a team of NE CASC researchers including Daniel Buonaiuto and Bethany Bradley suggests that improving the overall effectiveness of weed risk assessments begins with evaluating the utility of their individual criteria. Their work was recently published in Conservation Letters.

Many assessments include a question asking whether a species has close relatives that are already invasive. However, it is unclear how helpful this information is, and we don't know which levels of taxonomy (like genus or family) are the most useful for predicting risk. To address this question, the authors developed a series of statistical models that predicted how likely a species was to be invasive if it had known invasive species in its family or genus--or if its closest relative was invasive. This relatedness information improved the ability to predict invasion risk, and the authors suggest that asking this question at the genus-level is best for risk assessments. They also highlighted that models were not effective at identifying invasion risk in particularly small or large genera, indicating that there is room for regulators and evolutionary biologists to collaborate on developing more powerful and accessible tools to screen for invasive species.