Life after establishment: factors structuring the success of a mountain invader away from disturbed roadsides

Climate change and increased anthropogenic activity may both alter the current ranges of non-native plant species in mountainous areas, and could result in increased success of such species at higher elevations in the future. However, the course that management should take is often unclear due to a lack of information about the dynamics of how successful mountain invaders spread away from roadsides. The goals of this study were to determine if patterns of growth of a successful mountain invader, Linaria dalmatica (L.) Mill., (as measured by species cover) were: (1) similar to those of establishment (as measured by probability of occurrence), and (2) structured by the extant plant community. Study sites were established throughout the current elevation range of L. dalmatica in the Greater Yellowstone Ecosystem, and cover of the species was measured along with several vegetative community characteristics. Elevation influenced probability of occurrence (i.e., chance of establishment) for L. dalmatica, but not cover (which represents growth after establishment). L. dalmatica cover was negatively associated with several vegetative community characteristics which did not appear to be influenced by the presence of L. dalmatica. These results suggest that L. dalmatica establishment may be limited by climate, but that spread of established populations away from roadsides is most influenced by properties of the vegetative community. They further suggest that the resident vegetative communities structure the abundance of this invader, and that to limit spread of this species in mountainous areas, disturbance to the existing vegetative communities should be minimized.