Phylogenetic relationships of invasive plants are useful criteria for weed risk assessments

Risk assessments are conservation tools used to prevent the introduction of invasive species. Many assessments ask whether a taxon has invasive close relatives, but it is unclear whether this phylogenetic information is useful, and which taxonomic scales (e.g., genus, family) are most predictive of risk. Combining phylogenetic clustering analyses with models predicting invasion risk, we found invasive plants were clustered within nonnative flora of the conterminous United States. Taxonomic information in models improved their predictive capacity; invasion risk for taxa with invasive confamilials, congeners, or sister taxa increased by 9%, 16%, and 19% respectively. Phylogenetic information did not improve inference for species without any congeners, or those from large genera. The most common approach-assessing congeners-is well suited to identify invaders, particularly for genera with 2-10 established species. While existing phylogenetic information can enhance assessments of invasion risk, biologists and regulators should collaborate to improve nonnative species phylogenies.