Invasion biology and parasitic infections

Parasitic infections can strongly affect invasion success and the impact of invasive species on native biota. A key mechanism facilitating invasion is escape from regulation by natural enemies-the enemy release hypothesis. The level and duration of release depend on the types of parasites lost and gained, with highly regulating acute infections most likely to be lost and, over time, pathogenic RNA viruses likely to be gained. The rate at which hosts accumulate parasites depends on multiple factors, including the biotic re sis tance of the community and the ecosystem changes induced by the invasive species themselves. We discuss several examples of how invasive species may increase parasite susceptibility of the community by increasing parasite reservoir densities or by altering parasite fl ow via apparent competition. We then consider the evolutionary implications on a longer time scale if the susceptibility of invasive species is enhanced by loss of parasite re sis tance. Finally, we discuss whether parasites should be considered a special class of invader and conclude by identifying approaches, challenges, and priorities for future research in parasite dynamics of introduced species.