Parasite as a leading indicator for the healthy ecosystem

Background/Question/Methods

Unlike human health, which often depicted as a disease-free status, ecosystem health emphasis structural integrity and well-functioning of whole biological community. As more studies now consider parasite as an inimitable part of ecosystem, increasing evidences suggested that parasites mediated ecological processes at multiple hierarchies ranging from individual to ecosystem level. While influences from parasites on their hosts are well recognized, it is less apparent how parasites would respond to the fluctuations of non-parasitic community.

Results/Conclusions

Here, we conducted a simulation experiment using empirical food web data with/out parasites to elucidate how parasites react to primary species loss in ecosystem, as well as parasite’s influences on network robustness of community food webs. Our results indicated, regardless the variability of network complexity and preferential parasitism, the reductions in network robustness of food webs is mainly contributed by the complex life cycle constrain of parasites. It meant the existence of every complex life cycle parasite in the community represented at least one intact food chain in the ecosystem. Moreover, we showed that parasites are prone to secondary extinctions, which resulted from primary species loss, and their extinctions occur earlier than those involving non-parasitic species. Thus, we concluded that the vulnerability nature of parasite to species loss designates parasite an ideal leading indicator for structural integrity of a well-functioning food web, namely, a healthy ecosystem.