Disruption of Parasite-Host Interaction Networks: the role of key hosts.

Biodiversity loss is a threat to ecosystems for potentially triggering cascades of extinctions that compromise the stability of ecological communities. Host-parasite interaction networks are particularly sensitive to host extinction and represent a significant portion of biodiversity. This study investigates the structural robustness of two distinct small mammal-parasite networks in the Neotropical region: (i) generalist protozoan parasites and (ii) specific nematode parasites. By using sequential host removal simulations based on centrality metrics (degree and betweenness) we compare the decay of parasite richness and network fragmentation with random extinction scenarios. Our results demonstrate that targeted removal of key hosts significantly accelerates network collapse compared to random loss (P < 0.001 in all scenarios), showing that network stability depends on a small number of highly connected species. The protozoan network proved more vulnerable to fragmentation, while the nematode network was more sensitive to the loss of parasite diversity when the most connected hosts were removed. These results highlight the importance of considering network structure and the topological roles of species in conservation strategies, as the loss of key hosts can have disproportionate consequences for maintaining parasite diversity and ecosystem integrity.