The role of ecological opportunity in shaping host-parasite networks.

Despite the great interest to quantify the structure of host-parasite interaction networks, the real influence of some factors such as taxonomy, host body size and ecological opportunity remains poorly understood. In this paper, we investigate the general patterns of organization and structure of interactions in two anuran-parasite networks in the Brazilian Pantanal (seasonally flooded environment) and Atlantic Forest (non-flooded forest). We present theoretical models to test whether the structures of these host-parasite interaction networks are influenced by neutrality, host taxonomy and host body size. Subsequently, we calculated metrics of connectance, nestedness and modularity to characterize the network structure. We demonstrated the structure networks were influenced mainly by body size and taxonomy of the host. Moreover, our results showed that the seasonally flooded environment present networks with higher connectance/nestedness and lower modularity compared to the other environment. The results also suggest that seasonal floods may promote ecological opportunities for new species associations.