Basic Mechanisms and Evolution of Acoustic Communication

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Gerhardt, Carl IBN-9507394 Title: Basic Mechanisms and Evolution of Acoustic Communication Abstract The main goal of gaining knowledge about basic mechanisms and evolution of acoustic communication will be accomplished by studying members of the gray treefrog complex as a model system. Males of these treefrogs produce a small set of stereotyped, unlearned signals, and females base their choice of mates entirely on these signals. The use of synthetic, computer- generated sounds in playback experiments will be used to identify the exact acoustic criteria extracted from these signals by females from different populations throughout the range of the complex. A major selective factor that may shape differences between populations is the complexity of the acoustic community, and female selectivity will thus be compared between populations where two, genetically incompatible members of the complex co- exist with populations in which only a single species occurs. Further experiments will explore the effects of increasing acoustic complexity (background noise and number of competing signalers) on intrapopulational mate choice. Finally, the gray treefrog complex consists of three lineages of tetraploids that have acoustic signals with similar acoustic structures. Because these lineages are thought to have arisen independently and in one generation by autopolyploidy (doubling of chromosome numbers caused by environment factors), the question of how they achieved behavioral isolation from their diploid ancestors arises. The hypothesis that the changes in cell size and number that accompanies autopolyploidy have behaviorally important effects on call structure, female-choice criteria, or both will be tested by creating artificial polyploids from the cold-shocked eggs of diploid individuals.