What makes invasive species successful, and how do they affect native populations and communities? I addressed these key questions in the context of the invasion of Atlantic coral reefs by Pacific red lionfish (Pterois volitans). To assess the role of parasites in contributing to the success of this invasion, I compared infection rates of lionfish with syntopic carnivorous fishes at multiple locations in both the invasive and native ranges of lionfish. Invasive Atlantic lionfish had extremely few parasites when compared both to native Pacific lionfish and to ecologically similar native Atlantic reef fishes. Such “enemy release” may help to explain this successful invasion if lionfish consequently allocate more energy to growth and reproduction than to costly immune defenses. With few parasites limiting them, lionfish may consume ecologically important species, including Elacatinus spp. cleaning gobies: ubiquitous, conspicuous fishes that remove ectoparasites from other reef fishes. Although juvenile lionfish ate cleaner goby (E. genie) during laboratory experiments, they quickly learned to avoid them, likely due to a previously undescribed skin toxin in these gobies. Field experiments further revealed no change in the survival and growth rates of newly recruited cohorts of the cleaner goby in the presence vs. absence of lionfish. However, lionfish caused declines in the densities of the most abundant facultative cleaner, juvenile bluehead wrasse (Thalassoma bifasciatum), and of transient fishes that are often cleaned while visiting coral patch reefs. Therefore, lionfish do not have uniformly negative effects on native species; distasteful to potential predators, the cleaner goby is among the remarkably few small fish to escape predation by lionfish. The continued presence of Elacatinus spp. cleaning gobies, the predominant cleaners on invaded reefs, should limit cascading effects of lionfish on other Atlantic coral-reef inhabitants. Nonetheless, given their broad and voracious appetites, invasive lionfish will likely continue to affect native reef communities via predation on other cleaners and ecologically important fishes
