Studying the sensory ecology of frog-biting midges (Corethrellidae: Diptera) and their frog hosts using ecological interaction networks

Investigating species interaction networks has advanced the understanding of the robustness of ecosystems, the impact of species invasions, resource partitioning and the coevolution of interacting species. Here, we present a 10-year study of the relationships between frog-biting midges (Corethrella) and their frog hosts in tropical lowland forests across northern Borneo. We use quantitative bipartite host-ectoparasite networks to explore this unusual relationship. Across northern Borneo, nine species of frog-biting midges were found to bite 29 species of frogs. Overall, 378 individual Corethrella were found on 93 individual frogs. We compare the network structure between two forest types in Brunei Darussalam: a lowland mixed-dipterocarp rainforest and a peatswamp forest. Results indicate that both antagonistic interaction networks were relatively specialized at the community level and show significant nestedness. The degree of specialization was higher in the rainforest than in the peatswamp suggesting higher diversity of midge sensory perception and frog avoidance strategies in the rainforest. At the species level, the specialization of midges as well as their frog hosts was highly variable in both networks suggesting that some frog species are better at avoiding being bitten by Corethrella than others. Frog species parasitized by midges had calls of low dominant frequencies suggesting that the spectral bandwidth of hearing in midges could influence host selection. Despite this, some frog species that call above 4 kHz have not escaped parasitism. We explore the role of habitat filtering, behavior and coevolution in shaping network structure.