Agronomic non-native species are overrepresented across habitat types in central Canada

In response to non-native plant invasions, many governments have established noxious weed lists to control and eradicate introduced invasive plants. However, invasive agronomic species are often unregulated, and the extent of their invasion across habitat types has never been determined. Using vegetation surveys across 222 plots, we investigated the contribution of agronomic versus noxious non-native species to the levels of invasion across seven habitat types in central Canada. Although agronomic non-native species, such as Poa pratensis and Bromus inermis, only made up 21.3% of the non-native species pool, they accounted for 43.6% of non-native plant species frequency and 74.4% of relative non-native plant cover. They were also disproportionately overrepresented compared with noxious non-native species across all habitat types, except saline marshes. The overabundance of agronomic non-native plants in central Canada is likely the legacy of cultivar breeding, intentional seeding of introduced forage species and a lack of incentive for the use of native species. Synthesis and applications: Decelerating the invasion by agronomic non-native plants will require approaches beyond noxious weed lists and initiatives in research, policy and education. These tools can include incentives to use native seed material, for example, in reclamation and forage and turf production, to reduce propagule pressure from invasive agronomic non-native plants. Decelerating the invasion by agronomic non-native plants will require approaches beyond noxious weed lists and initiatives in research, policy and education. These tools can include incentives to use native seed material, for example, in reclamation and forage and turf production, to reduce propagule pressure from invasive agronomic non-native plants.image