Some evidence (particularly in anurans) suggests that neutral processes are also important for signal divergence. Over the past few decades, the effects of the ecological (environmental) context and mate choice pressures on acoustic signals have been focal points of research in the bioacoustics of animals. Several evolutionary mechanisms are major drivers of acoustic divergence, including neutral and mutation-order processes as well as natural and sexual selections. Revealing the mechanisms that result in signal divergences is a relevant topic in the evolutionary ecology of animals that use acoustic signals. These findings may help us understand how noise in the environment can influence natural selection as it shapes acoustic signals in affected species.Īcoustic signals are important behavioural traits in species delimitation, reproductive isolation, and animal communication. For instance, these anurans tend to generate vocalizations with less well-defined FM and harmonic traits. Our results may support AAH predictions in frogs that vocalize in noisy habitats because flowing-water environments often produce persistent ambient noise. Likewise, our results suggest that flowing-water habitats can constrain the evolutionary trajectories of the frequency-contour traits of advertisement calls in these anurans. We also showed that species living in lentic habitats tend to have advertisement calls characterized by well-defined FM and harmonics. ResultsĪfter including temperature, body size, habitat type and phylogenetic relationships, we found that DF differences among species were explained mostly by body size and habitat structure. By using data from 106 species in these clades, we focused on the characterization of the differences in dominant frequency (DF) and frequency contour (i.e., frequency modulation and harmonic performances) of mating calls and compared them between species that inhabit flowing-water or still-water environments. Here, we explored this effect by including an environmental noise dimension to test some AAH predictions in two clades of widespread amphibians (Bufonidae and Ranidae) that actively use acoustic signals for communication. These studies, based on the AAH, predict that acoustic signals should experience less attenuation and degradation where habitats are less acoustically complex.
To date, most AAH studies have focused on the effect of stratified vegetation on signal propagation. The acoustic adaptation hypothesis (AAH) states that signals should evolve towards an optimal transmission of the intended information from senders to intended receivers given the environmental constraints of the medium that they traverse.
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