Exotic species influencing native parasites: a cause for concern?

PATERSON, R.; RAUQUE, C.; TOWNSEND, C.; POULIN, R.; TOMPKINS, D.

Bariloche, Argentina

Congreso; VI Southern Connections Congress.; 2010

·         Exotic species can have deleterious effects on native biodiversity, particularly involving predation and competition, but have been increasingly implicated in disease impacts on native species. Recent studies have demonstrated strong effects of parasite spillover, whereby native species are exposed to new parasites from exotic hosts. However, exotic species may also acquire native parasites and have the potential to alter native parasite dynamics by acting as infection reservoirs (spillback) or sinks (dilution) or cause no change. Our research has focused on native parasites of native and exotic freshwater fish in New Zealand and Argentina. We aimed to determine how the presence of exotic hosts influences the dynamics of native fish parasites. We conducted a combination of field surveys and laboratory experiments involving native and exotic hosts, and constructed dynamic community models to examine the influence of exotic species. We have demonstrated two of the potential outcomes of exotic species acquisition of native parasites and have established the main factors that determine whether parasite dynamics are modified. Host competency for native parasites was essential in determining the occurrence of spillback and dilution, but other factors (e.g. host density) may alter the influence of exotic species on disease in native fish. Our research highlights a seldom-recognised mechanism involving host-parasite dynamics by which exotic introductions can impact native species.