Beyond the Croak: Decoding the Silent Communication of Frogs

Abstract

Frogs rely on vocal signals for social interactions, which depend on a functional auditory system. Yet multiple lineages have independently lost critical auditory structures, raising questions about how communication is maintained. We hypothesized that visual adaptations could compensate for reduced auditory capacity. To test this, we measured eye and corneal size across 264 anuran species and assessed associations with ecological traits and auditory condition. We also sequenced the genome of Pristimantis brevicrus, an earless species, to examine the molecular evolution of visual opsins. Species with auditory reductions had smaller eyes, but non-fossorial taxa exhibited enlarged corneas, enhancing light sensitivity at lower metabolic cost. Analyses of RH1, SWS1, SWS2, and LWS revealed predominant purifying selection, while species with auditory loss showed relaxed constraint and positive selection, particularly in SWS1 and LWS. These findings suggest that visual adaptations compensate for auditory loss, highlighting sensory trade-offs as drivers of anuran communication and evolution.