Divergence in mating signals predicts behavioral responses among three closely related species of wrens in the genus Campylorhynchus

Description

ur research hypothesis posited that vocal divergence among Campylorhynchus humilis, C. rufinucha, and C. capistratus functions as an effective premating barrier, facilitating species recognition and reinforcing reproductive isolation. To test this, we conducted playback experiments, a method that directly assesses behavioral responses to conspecific and heterospecific vocalizations. Songs from each species were recorded in their respective habitats, standardized for playback quality, and broadcast to individuals in the field. Behavioral responses were quantified using metrics such as approach distance, vocal replies, and aggression displays. The data revealed species-specific responses, with all three species reacting significantly more strongly to conspecific songs than to heterospecific or control playbacks. Notably, C. humilis and C. rufinucha exhibited pronounced reactions to conspecific playbacks, suggesting strong reliance on vocal cues for species recognition. In contrast, C. capistratus displayed consistently weaker responses across all treatments, which may indicate reduced reliance on vocalizations or alternative mechanisms for recognition. These findings align with genetic, morphological, and vocal divergence patterns previously documented for these taxa, supporting the hypothesis that vocalizations play a pivotal role in delineating species boundaries. The data suggest that song divergence in allopatric populations is a key factor in maintaining reproductive isolation. This underscores the broader evolutionary significance of acoustic signals in avian speciation and highlights the utility of playback experiments as a tool for assessing species limits and understanding the mechanisms driving speciation. Researchers can use this approach to further investigate the interaction between vocal divergence, ecological context, and evolutionary processes in other avian systems.

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