Cyanobacteria as facilitators for benthic macroinvertebrates: assessing factors involved in the establishment and conservation of aquatic interactions and biodiversity in tropical rivers in Mexico

Abstract Interactions between organisms of different trophic levels are not only involved in the functioning of aquatic systems such as rivers but also crucial to maintaining taxonomic and functional diversity. This study aimed to evaluate the diversity of benthic cyanobacteria and their role as facilitating species for the colonization of benthic macroinvertebrates (MIB) in tropical mountain rivers with varying ecological conservation statuses. We sampled ten river segments in central Mexico, assessing physical and chemical parameters and collecting macroscopic cyanobacterial growths. A taxonomic and morphofunctional characterization was conducted for both biological groups, while a land-use change index (CDI) was calculated to assess the ecological quality of the sites. The analysis of similarities (ANOSIM) showed that cyanobacterial taxa are the factor that determines significant differences in the composition of MIB assemblages, with Cricotopus , Tanytarsini, Simulium , and Baetis being the most representative taxa according to the similarity percentage analysis (SIMPER). We also constructed an interactions network comprising eight cyanobacterial and 32 MIB taxa. The dominance of dipterans reflects substrate specialization, while the prevalence of collector morphologies suggests indirect food acquisition. While MIB were observed in unilateral associations with filamentous cyanobacteria, they formed multilateral associations with colonial species. Cricotopus showed a preference for both Nostoc tlalocii and Cyanoplacoma aff. regulare , revealing nonexclusive mutualistic relationships. This study demonstrated that cyanobacteria are important substrates for MIB to complete their life cycle, including the use of different species that are similar in their level of organization and therefore thallus morphology. This interaction network demonstrates adaptability, with some interactions being nonexclusive. Substrate turnover and voltinism in MIB may be linked to resiliency in the face of habitat changes caused by anthropogenic activities in the studied river basins.