Abstract
The matched filter hypothesis proposes that the tuning of auditory sensitivity and the spectral character of calls will match in order to maximize auditory processing efficiency during courtship. In this study, we analyzed the acoustic structure of male calls and both male and female hearing sensitivities in the little torrent frog (Amolops torrentis), an anuran species who transmits acoustic signals across streams. The results were in striking contradiction to the matched filter hypothesis. Auditory brainstem response results showed that the best hearing range was 1.6–2 kHz consistent with the best sensitive frequency of most terrestrial lentic taxa, yet completely mismatched with the dominant frequency of conspecific calls (4.3 kHz). Moreover, phonotaxis tests show that females strongly prefer high‐frequency (4.3 kHz) over low‐frequency calls (1.6 kHz) regardless of ambient noise levels, although peripheral auditory sensitivity is highest in the 1.6–2 kHz range. These results are consistent with the idea that A. torrentis evolved from nonstreamside species and that high‐frequency calls evolved under the pressure of stream noise. Our results also suggest that female preferences based on central auditory system characteristics may evolve independently of peripheral auditory system sensitivity in order to maximize communication effectiveness in noisy environments.
Highlights
Animal communication involves transmission of complex signals from senders to receivers
Anurans, birds, and mammals, acoustic signals play an important role in coordinating reproductive behavior (Gerhardt & Huber, 2002; Rogers & Kaplan, 2000)
In acoustic communication systems, auditory tuning generally tends to evolve toward improving the detection of biologically relevant acoustic signals in the natural environment
Summary
Animal communication involves transmission of complex signals from senders to receivers. In acoustic communication systems, auditory tuning generally tends to evolve toward improving the detection of biologically relevant acoustic signals in the natural environment This reduces the probability of interactions occurring which can reduce the fitness of reproductive individuals such as hybridization and competition for a communication channel (Pfennig & Pfennig, 2009; Ritchie, 2007; Ryan & Rand, 1993). Female phonotaxic behavior is a useful method for evaluating female preferences and can be used as a proxy for evaluating how intersexual selection may have acted on male calls For these reasons, we compared female phonotaxic responses to call playbacks with the DF of the calls adjusted to that of the best hearing sensitivity (which was relatively low) versus calls whose DF was adjusted to the natural call frequency of males (which was relatively high) in the presence of three levels of stream noise as described below, in order to determine. | 421 whether the female behavioral response was influenced by the background noise context
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