Specialization in Ciidae-host fungi communities in two Atlantic forest remnants of Southeast Brazil

Mycophagy, the practice of feeding on fungal structures or plant material decomposed by fungal enzymes, is one of the oldest feeding habits of beetles. A notable family of beetles with a strict association with fungi throughout their life cycle is Ciidae. Members of this family use fungi as shelter, food, and sites for copulation and oviposition, making them true mycetobionts. The fungi associated with ciids belong to the phylum Basidiomycota and play a crucial role in nutrient cycling by degrading wood and decomposing cellulose, hemicellulose, and lignin. Ciids contribute significantly to the degradation of these basidiomes, thereby preventing their accumulation and enhancing nutrient availability in forest ecosystems. Although interactions between Ciidae beetles and their host fungi have been relatively well-studied, research on these interactions in the neotropics remains scarce. In this study, we investigated the interactions between ciids and their host fungi in two forest remnants of the Atlantic Forest biome. Using ecological network analysis, we assessed the frequency of occurrence of ciid species and calculated key indices for describing community structure: connectance, web asymmetry, links per species, nestedness, robustness, and specialization. This allowed us to compare the structural patterns of the two Ciidae-fungi networks. Our results revealed that the main host fungal species were the same in both communities, but differences in host usage by ciids were observed, reflecting the availability of fungal basidiomes. These differences led to distinct network structures. Most Ciidae species were found to be generalists, exploiting host fungi according to their availability.