Parasite invasions and impact potential

Parasitism is an important predictor of biological invasions. The presence or absence of parasitic organisms can affect how invasive alien species (IAS) become established in a new region, spread within or between regions, or impact native species post-establishment. However, despite their importance, parasites are often overlooked when addressing the potential ecological and/or environmental impact of invaders. In this chapter, we utilize the Relative Impact Potential (RIP) metric, which combines per capita feeding rates (i.e. functional response), with population abundance estimates, in order to predict the total potential impact of IAS, relative to native comparators. Using the RIP metric, we examine multiple published case studies, for which parasitism has been shown to contribute to invader impacts, and explore how parasite prevalence can enhance, or reduce, impact predictions. We propose modifications to the RIP metric, which, in conjunction with comprehensive parasite screening, could provide a more encompassing assessment tool.