Michael J. Ryan
Dept. of Zool., Univ. of Texas, Austin, TX 78712
The efficiency of communication can be maximized by a tight match between signal and receiver. This view underlies the field of animal communication and has led biologists to propose functional and evolutionary models that are firmly grounded in such linkage. Recent empirical studies have shown, however, that tight linkage between sender and receiver need not be the case. Using the phonotactic response of female frogs to variation in mating calls, it has been shown that some aspects of the receiver are quite broad relative to the conspecific signal. For example, females show preferences for signals of their own species to which are added components from the signals of other species. Also, using algorithms for reconstruction of ancestral traits, it is shown that key stimuli needed for species-specific pattern recognition have not been tightly linked with receiver evolution. These studies suggest a more liberal interpretation for the evolution of animal communication systems.