Understanding patterns and pathways of exotic perennial grass invasion in South‐eastern Australian grassy communities

Aim Exotic perennial grasses (EPGs) are significant invaders of native grassy communities. We sought to determine how the profile of invading perennial grasses varies among different climatic regions and different grassy communities, to understand at which scale management is best undertaken. We investigated whether invader occurrence was related to specific plant traits. Location New South Wales, Australia. Method Field surveys of EPGs at 139 sites from nine grassy communities across four regions were assessed for variation in invasion profiles amongst regions and communities. We used a ranking of invasion risk based on plant characteristics to identify grasses likely to be more invasive and tested whether this ranking predicted the level of invasion in the survey. Results Using multivariate analysis, we found that all communities were significantly invaded. These assemblages were distinct regionally, and for most plant communities. Five widespread invaders were established in all regions and communities. Invasion by pasture grasses (termed trade‐off species) was the most significant threat, coupled with capacity to develop long‐term seed banks and use allelopathy. Species with higher risk rankings were recorded in more sites, although a few grasses had much greater occurrences than their ranking predicted. Conclusions Grassy communities across all regions were invaded by a suite of EPGs, some that have not been considered as problematic previously. Higher levels of invasion were associated with higher ranked species based on plant traits, indicating that our risk assessment is valuable as a management prioritization tool. Findings support community level management, although some species are important widespread invaders and could be managed at larger scales. Differences in species assemblages compared to nearby agricultural areas confirm different invasion pathways, with significant invasion from pasture grasses. Aided by the risk assessment tool, we propose that EPG management in native communities considers the climatic, community (including surrounding) and species level for prioritization.