The establishment and persistence of complex life cycle parasites are generally thought to be regulated by free-living host diversity, and the stability of ecological interactions.  In this study, we test the prediction that stable host communities are a requirement for complex multi-host parasite life cycles to establish.  Using salt marsh sites representing a gradient in host species diversity, and time since major ecological restoration, we document the colonization of naïve killifish, Fundulus heteroclitus, by parasites with complex or direct (one host) life cycles.  

Results/Conclusions

We demonstrate that the diversity of the parasite community, and the rate at which species accumulated, were similar for the unrestored, and the 10- and 20- year restored marsh sites whereas, the parasite community in the newly restored marsh (0 year) supported only directly-transmitted parasite species.  To explain the paradox of a low diversity, highly invaded salt marsh (unrestored) having the same parasite community as highly diverse restored marsh sites (10 and 20 yrs) we assessed community stability using community matrices with randomly determined interaction coefficients.  We find a correlation between system stability and parasite species richness, and identify a threshold above which complex life cycle parasites are able to establish.  These results suggest a role for host community stability in parasite community assembly, and support the idea that stable trophic relationships are required for the persistence of complex parasite life cycles.