Acoustic Signal Evolution: Biomechanics, Size, and Performance
The interface of proximate and evolutionary perspectives can provide fundamental insights into acoustic signals and their evolutionary diversification. This chapter focuses on three facets of acoustic mechanisms-biomechanics, size and performance-each of which bears upon patterns of signal evolution. Our discussion of biomechanics focuses on the mechanics of sound production across the katydids. We show that the integration of biomechanics and phylogeny-based analyses is yielding new and unexpected explanations for the generation of extremely high frequency signals, the transition from tonal to broadband signaling, and the relationships between signal features and mating strategies. Our discussion of acoustics and body size, focuses in on the evolution of acoustic frequencies. We propose that many of the most informative relationships between size and acoustic frequency occur at the level of the sound producing apparatus itself, rather than at the level of the whole body. Finally, we discuss performance in signaling mechanisms, focusing especially on acoustic tradeoffs experienced by singing birds. By pushing bird signal features to the limit, even the most fundamental features of song, such as frequency bandwidth and trill rate, can shape signal expression at both developmental and evolutionary timescales. Exploring these factors in acoustic signal evolution helps delimit the range of signaling structures possible, and thus complements more traditional analyses of signal evolution that focus on costs and reliability.
