Antagonistic Rewiring and Turnover Patterns in a Neotropical Fish–Parasite Metanetwork

ABSTRACT Integrating beta‐diversity and network analyses is an emerging approach for understanding the spatial structure of species communities. For instance, although the presence of hosts affects parasite species distribution, environmental factors can either restrict or promote the occurrence of certain parasite species by changing the abundance of suitable hosts or by affecting the free‐living stages of some parasite groups. Here, we combined the metacommunity framework with network analyses to address two main questions: (1) How do fish–parasite interactions respond to a longitudinal gradient along a river? and (2) Which ecological descriptors are associated with species' roles in metanetwork connectivity? We explored the beta‐diversity patterns of fish–parasite interactions along a Neotropical River gradient and analysed how species contribute to the connectivity of the river metanetwork. To achieve this, we investigated the association between network centrality descriptors of fish and parasite species and their ecological and quantitative traits. We found a high turnover of both species and interactions along the river's longitudinal gradient, as well as a rewiring of interactions in adjacent river stretches. Different environmental factors shape this gradient, and our results suggest niche‐based processes are driving the observed interaction patterns. Interaction turnover was positively correlated with geographical distance, and evidence of rewiring in response to anthropogenic impacts was observed throughout the river. The analyses of species roles and their contribution to river connectivity were complementary to the beta‐diversity findings, elucidating patterns of parasite sharing along the river. Parasite species with higher mean abundances were more likely to persist across different river stretches, and non‐adult parasites had a greater probability of infecting multiple host species. Additionally, fish species belonging to the same taxonomic order and exhibiting similar trophic habits were more likely to share parasite species. We demonstrated that fish–parasite interactions follow a deterministic pattern, and as such, habitat changes across river stretches had a stronger influence on the metanetwork than would be expected by chance. These results underscore the importance of preserving the natural gradients of river systems and controlling the anthropogenic pressures that might alter interaction dynamics in aquatic environments.