Several studies have been carried out to evaluate the main drivers behind biological invasions and their ecological consequences. Nevertheless, it is still extremely difficult to acquire a full understanding of the invasion process due to its high level of complexity. The problems that complicate invasion studies are low detection during the early stages of invasion, and the high survey cost of working over large, inaccessible, and rugged areas. The studies that develop efficient tools to reduce costs and time will help to control or mitigate the invaders' damaging effects. Hieracium pilosella is an aggressive invader of grasslands worldwide. The aim of this work was to conduct a regional assessment for the suitability of H. pilosella invasion in the Fuegian Steppe by combining field surveys, spatial modeling, and geographic information system tools. We recorded the invader cover in 167 sample sites and we determined the relationship between environmental variables and the probability of invasion. This was carried out by the selection of alternative generalized linear models. The best model indicates that disturbance and plant community were the main drivers to predict invasion suitability on a regional scale. Therefore, these two variables were used as main inputs to construct a regional invasion suitability map, which identifies the most critical areas for prevention, control, and further monitoring. This approach corresponds to a tool that permits us to evaluate the suitability of invasion even over large and inaccessible areas. The results especially warn about soil disturbance associated with usual management practices in Fuegian rangelands.

Nomenclature: Mouseear hawkweed, Hieracium pilosella L.

Management Implications: Habitat suitability evaluations have been used for several scientific or management issues. They have been particularly useful in the ecology of invasions, to evaluate the effect of different environmental variables regarding invader spread and population dynamics. The approach presented in this work integrates field surveys, spatial modeling, and GIS tools to assess the suitability of invasion in an early stage of the invasion process, and over large areas. Even more, fieldwork effort and cost can be reduced, allowing for a more effective invasion detection, control, and monitoring.