Acoustic Signal Evolution: Biomechanics, Size, and Performance

Allometry of male sound‐producing structures indicates sexual selection on wing size and stridulatory teeth density in a bushcricket

“…The proposed positive selection on wing size may correspond to the functional consequences of larger size for the acoustic parameters in a male's song. Larger sound‐generating organs are generally associated with the production of lower‐frequency signals (Bennet‐Clark, ; Podos & Patek, ), a common pattern also found comparing species of bushcrickets (Del Castillo & Gwynne, ). This pattern needs still to be verified in our species, as a study in crickets detected increasing sound apparatus sizes with larger male body size, but was unable to detect an association with song frequencies (Miyashita et al ., ).…”

“…Female choice of heavier males is adaptive, as females energetically benefit from consumption of the nutritious spermatophylax (Voigt et al ., , ; Lehmann & Lehmann, ). The development of larger wings, a longer stridulatory file and larger stridulatory teeth, however, might be constrained by several factors like the costs of sexually selected features (Simmons et al ., ; Podos & Patek, ), genetic covariance with other traits and the resources available during ontogenesis (Bonduriansky, ). Bushcricket males face high costs in producing the nuptial gift, which in P. ampliatus represents 20% of a male's body mass (Lehmann and Lehmann, unpublished data).…”

“…Songs can be considered as honest signals (Grafen, ) and their acoustic structure might change depending on male quality and physical characteristics of sound generator organs (Bennet‐Clark, ). Males with poorer body condition produce less efficient signals, compared to males of higher body condition (Podos & Patek, ).…”

“…Moreover, the file‐tooth arrangement may affect the sound component such as the amplitude (Montealegre‐Z & Mason, ). The fundamental frequency is one of the most important features of the song and is mainly defined by speed of the wing movement and the spacing of teeth along the stridulatory file (Podos & Patek, ). Males with large‐dimension sound‐generating organs are able to produce low‐frequency sound, whereas males presenting smaller organs are emitting songs with higher frequencies (Bennet‐Clark, ; Podos & Patek, ).…”

Bark beetles use a spring-loaded mechanism to produce variable song patterns

“…The functional significance of signal variability has been well documented; different signals can convey a variety of messages, or enhance the efficacy of transmission in different environments (Balakrishan, 2016;Gerhardt and Huber, 2002;Greenfield, 2002). Comparatively little is understood about the underlying neural and mechanical controlthe proximate mechanismsrequired to produce different signal types (Podos and Patek, 2014). Yet, such mechanisms are the basis upon which selection acts and are therefore important for understanding the evolution of communication (Podos and Patek, 2014).…”