© 2002 by The Society for Integrative and Comparative Biology
Acoustic Communication in Insects and Anurans: Common Problems and Diverse Solutions
1 Neurobiology, Physiology and Behavior, University of California, Davis, One Shields Avenue, Davis, California 95616, E-mail: avhedrick{at}ucdavis.edu
Acoustic Communication in Insects and Anurans: Common Problems and Diverse Solutions. H. CARL GERHARDT AND FRANZ HUBER. The University of Chicago Press, Chicago and London, 2002, 531 pp. (paper, ISBN 0-226-28833-1).
Cicadas, orthopterans (crickets, katydids, and grasshoppers), and anurans (frogs and toads) are among the animals that Darwin (1871)
described as having "musical powers." Insects and anurans are only distantly related, yet their acoustic communication shares many features. For example, both groups use acoustic communication to bring the sexes together for mating, and both can perform their songs perfectly the first time without learning them from other individuals (which is not true of most birds). Many insects and anurans sing in large aggregations. Finally, biologists interested in the production, sensory reception and function of animal sounds have studied communication in insects and anurans intensively for the last 50 years.
An ambitious new volume by Gerhardt and Huber ably summarizes this work. Both authors are distinguished specialists in the field of animal communication: Gerhardt on the behavior and evolution of anurans, and Huber on the behavior and neurobiology of insects. The book highlights both the parallels and contrasts between anuran and insect communication, and attempts to integrate the study of proximate mechanisms with that of ultimate function. Of the 10 chapters after the Introduction, the first six are devoted almost entirely to physiological mechanisms, and the final four almost entirely to behavioral ecology and evolution. In each chapter, boxes give details on key concepts and experiments. Figures and lengthy legends present much of the relevant data. The authors conclude each chapter with suggestions for future research—perhaps the most useful feature of this book.
The book begins by describing acoustic signals and signal repertoires in anurans and insects, and how sounds are produced in these taxa (Chapter 2). An interesting box discusses temperature effects on signals, which can influence communication in these ectothermic animals. The subsequent five chapters focus primarily on physiological mechanisms. They treat neural control of sound production, signal recognition and preferences, processing of acoustic signals in both the auditory periphery and central auditory systems, and sound localization. Many biologists have studied the neural control of sound production since Huber's pioneering work in the 1950s on command systems for stridulation in crickets. The book describes this newer work in detail, yet makes it clear that many questions remain, especially in anurans. Those who are following current debates about the evolution of female mating preferences will find many detailed examples in the chapters on signal recognition and preferences and sound localization, although they may be dismayed to find little here on the function of female preferences (this topic appears later in the book). Two chapters on signal processing emphasize how acoustic signals are encoded in the very different nervous systems of insects and anurans. These chapters introduce several repeating themes of the book- that the selectivity of neurons is not necessarily correlated with mate selection in the behaving animal, that mate selection in the "noisy" field environment may be much different than it is in the laboratory, and that we need more information on the details of mate choice in the field. For example, how long do females listen to alternative signals of males before making decisions?
The final four chapters of the volume are devoted primarily to the function of acoustic communication, and deal with chorusing, acoustic competition and alternative tactics, female choice for acoustic signals, and broad-scale evolutionary patterns. These chapters seem less thorough than the preceding seven chapters. Boxes would have been helpful to explain game theory (Chapter 9: acoustic competition and alternative tactics), stabilizing versus directional selection and models of sexual selection (Chapter 10: female choice based on acoustic signals), and methods of phylogenetic analysis (Chapter 11: broad-scale patterns of evolution). Still, these chapters offer some interesting insights and information. For example, the authors have compiled a large appendix summarizing the literature on female acoustic preferences, including the pattern of preference (e.g., medium pulse rate is preferred to high pulse rate), the presumed mode of selection (stabilizing or directional) and the type of experiment (two choices, no choices, etc.). They also argue convincingly that although signaling in insects is not as metabolically expensive as it is in anurans, it may nonetheless be constrained by energetic considerations, just as it is in anurans.
In the chapter summaries and throughout the book, the authors forthrightly state their opinions and suggestions for future work. They often challenge what they refer to as the current "dogma." For example, they question the "dogma" that acoustic experience during development is not required for normal sound production in insects and anurans. They also suggest that key observations and experimental data are missing from many current claims of satellite male behavior. Some readers will not agree with their assessments, but all readers will find that the book raises some provocative questions.
This book is not for the merely curious. It is densely written, and packed with technical details and complex figures. However, specialists and highly motivated beginners will find the wealth of information gathered here a tremendous resource.
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Darwin, C. 1871. The descent of man and selection in relation to sex. John Murray, London.
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