More than meets the eye: decrypting diversity reveals hidden interaction specificity between frogs and frog-biting midges

Abstract

1. Female frog-biting midges (Diptera: Corethrellidae) eavesdrop on the nocturnal mating calls of their blood hosts – male frogs. Available data suggest variable degrees of specialisation among Corethrella-host associations, with limited information on the mechanisms involved in host selection and partitioning on a community level. 2. Our study provides a first comprehensive analysis of host interactions for a neotropical community of frog-biting midges, based on both morphological and molecular genetic species delimitation. We used quantitative bipartite interaction networks to investigate host specificity among the midge-frog community of La Gamba, Pacific lowland Costa Rica. 3. Midges that were collected directly from frog hosts (16 frog species) showed more pronounced levels of specificity (network-wide degree of specialisation: H2′ = 0.3) than those caught with acoustic traps broadcasting their calls (12 frog species; H2′ = 0.08). This indicates that, despite a rather generalist acoustic foraging behaviour, frog-biting midges discriminate between potential hosts by using additional close-range recognition cues. 4. Based on COI and ITS2 sequencing data, we identified considerable levels of cryptic diversity within our five Corethrella morphotypes, with at least 17 distinct MOTUs of Corethrella in La Gamba. Including these MOTUs in bipartite network analyses produced higher resolution in species interactions, and increased estimators of network specificity (H2′ = 0.42).