Network analysis of co-occurrence patterns in macroinvertebrate communities in lentic and lotic ecosystems of the tropical Andes, Ecuador

Co-occurrence networks are highly useful tools for studying fundamental aspects of ecosystems and for measuring ecosystem resilience. This information is especially valuable for the poorly studied tropical Andean aquatic ecosystems. Hence, co-occurrence networks were identified across three aquatic systems of southern Ecuador using extensive macroinvertebrate datasets from tropical Andean rivers and lakes. Full, positive, and negative networks were characterised through 8 network metrics, whilst the centrality of graph nodes was assessed using 3 centrality indices. The Tomebamba River had the most complex network, followed by the Yanuncay River and the Lakes in CNP (Cajas National Park). Oligochaeta, Hydracarina, and Chironomidae were present in all ecosystems. Different key taxa were identified, including Heterelmis and Psychoda (Tomebamba River), Palpomyia (Yanuncay River), and Hyalella , Liodessus , and Chironomidae (Lakes in CNP). In general, negative associations were more frequent than positive ones (statistically), indicating that these ecosystems could be driven by strong selection, competition, or niche partitioning. Clustering, average path length, and modularity metrics across the three network types indicate that riverine communities were divided into distinct subcommunities with niche exclusion. In contrast, taxa within these subcommunities tend to cooperate. The flow serves as a conduit, shortening paths between different parts of the network and linking subcommunities. In the lakes, environmental conditions were stable, leading to the development of possible strict competitive boundaries among taxa. Since water movement is limited, these groups were poorly connected. Positive interactions were localised in the lakes. Understanding community interactions and driving forces, and identifying key taxa, could provide valuable information for management and conservation, especially amid rapidly increasing anthropogenic pressures in these high-mountain ecosystems.