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

Abstract

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.

The sound of a blood meal: Acoustic ecology of frog‐biting midges (Corethrella) in lowland Pacific Costa Rica

“…We found a close correspondence in the relative proportions of midges captured with acoustic traps (both trap types) and those collected directly from frog hosts (JV unpublished). Similar observations were made in peatswamps of Brunei (Grafe et al, ), suggesting that acoustic traps accurately reflect true midge abundances. Other methods, for example, resting boxes (Camp, ), could additionally be included in future studies to obtain more accurate estimations of midge abundances as well as species diversity.…”

“…Indeed, our preliminary analyses of midges collected directly from frogs show more pronounced host preferences, with some species showing a narrower host range than others (Virgo et al in prep.). In a recent study using ecological network analyses, Grafe et al () found both specialized and generalized midges when sampling on frogs in Borneo, suggesting that some frog species are better at avoiding being bitten by Corethrella than others.…”

“…C. ranapungens, the most common species overall, showed broad attraction to most acoustic stimuli presented. (Grafe et al, 2018), suggesting that acoustic traps accurately reflect true midge abundances. Other methods, for example, resting boxes (Camp, 2006), could additionally be included in future studies to obtain more accurate estimations of midge abundances as well as species diversity.…”

“…Although the ability to detect and exploit anuran advertisement calls likely has derived from a pre‐existing sensory bias (use of acoustic signals during swarming (Silva, Nutter, & Bernal, )), it seems likely that the corethrellid auditory system has adapted to maximize detection of frog hosts. However, the exact call parameters favored by selection are difficult to disentangle, and the extent to which those parameters differ between midge species and localities are essentially unknown (but see Grafe et al, ). In the present study, we aimed at identifying acoustic traits in frog calls that affect midge attraction around the La Gamba research station in Pacific lowland Costa Rica.…”

A new species of frog-biting midge from Papua New Guinea with a key to the described Corethrellidae of the Australopapuan region (Diptera, Corethrellidae, Corethrella)

“…Locating their hosts primarily by auditory cues (Borkent 2008, Bernal and de Silva 2015), they are an emerging study system in studying the ecology and evolution of acoustic eavesdropping behaviour (Bernal et al 2006, Grafe et al 2008, 2018, de Silva et al 2015, Caldart et al 2016, Legett et al 2018). Their fossil record extends back to the early Cretaceous and their ancient age is reflected in their biogeography which suggests Gondwanan vicariate events (Borkent 2008, Baranov et al 2016).…”