We are family: close relatives of invasives species are more likely to be invasive themselves
Buonaiuto, D. M., Evans, A. E., Fertakos, M. E., Pfadenhauer, W., Salva, J., & Bradley, B. A. (2023). Phylogenetic relationships of invasive plants are useful criteria for weed risk assessments. Conservation Letters, e12979. PDF
Written by: Dan Buonaiuto, edited by Sarah Bois
Summary
Weed risk assessments (WRAs) are tools used to regulate imported plants and quantify the risk that a new species may become invasive. All WRAs include a series of yes/no or ranked questions about the biology, ecology, and distribution of the species of interest, though the specific formats of these protocols vary substantially among the governments and agencies that administer them. As such, they have a mixed track record for successfully identifying new invaders. A new study by Buonaiuto et al. suggests that improving the general effectiveness of WRAs begins with evaluating the effectiveness of each of their criteria.
Many WRA include a screening question about whether a species has close relatives that are already invasive. However, we don’t know how helpful this information actually is, and we don’t know which levels of taxonomy (e.g., genus or family) are the best for predicting risk. To answer these questions, the authors of this study ran several phylogenetic analyses and 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.
The authors found that invasive plants were more likely to be closely related to each other than chance would have it, and that including information about species relatedness in models improved their ability to predict invasion risk. Models that included information on whether or not a species had other invasive species in its genus, and whether or not its closest relative was invasive performed the best. The authors suggest that because genus-level information is easiest to obtain, questions about taxonomic relatedness at the genus-level are best for WRAs. The authors also highlighted that none of their models were able to properly quantify invasion risk in particularly small or large genera, which indicates that there is a need for plant regulators and evolutionary biologists to increase collaborations in order to develop new screening tools for invasive species.
Take home points
Invasive plants are likely to be closely related to each other.
Management implications
Asking whether a plant species of interest has an invasive congener is a useful question in Weed Risk Assessments
Keywords: Invasive plant, Invasiveness, Phylogeny, Policy, Weed risk assessments