Auditory communication requires a sound call emitted by one animal to be received as a sensory signal and detected reliably by another animal listening. It is important to know how the receiver is matched to the signal in a given species, and how congruence can be maintained over generations despite the individual variability within a species. Nowhere is the match between signal and receiver more crucial than when the communication system is used in mate recognition. Females often use the signal from a calling male to discriminate between members of the same species versus other species, and if the male's signal does not match the female's detection properties he will be ignored as a potential mate. Neurobiology, behavior, morphology and evolutionary biology are combined here to study the "microevolution" of communication in particular populations of cricket frogs. The advertisement calls of males ready to mate will be quantified to see how pitch and timing of their acoustic components differ among the populations. Neurophysiological recording in the brain will be used to see how the auditory pathway processes call features that characterize the population. Behavioral studies will test whether females respond preferentially to calls from their local population. Variation within a population will be analyzed to see how differences affect mate choice, to identify sex differences in the communication system, and to see how the structure of the calling organ, the larynx, may constrain or promote call changes. Finally, genetic relatedness will be assessed biochemically to see if populations that are separated but share similar call structure reflect similar pressures from habitat constraints on acoustic signals, or instead reflect a historical ancestral relation- ship. This work represents a uniquely complete analysis of a particular communication system, likely to uncover fundamental patterns and processes underlying the neural and morphological control and evolution of vertebrate social behavior and communication. Its multidisciplinary scope is likely to produce a wide impact on many areas of biology.
