Geographic and genetic factors shape acoustic divergence and dialect-like variation of communication calls in the greater horseshoe bats

Among animal species that utilize acoustic signals for communication, including humans, acoustic divergence plays a crucial role in recognition, sexual selection, and speciation. Recently, bats have emerged as a model system for investigating acoustic communication due to their complex vocalizations. This study aimed to demonstrate the dialects and related driving forces in communication calls of greater horseshoe bats (Rhinolophus nippon). We analyzed the communication calls collected from nine populations across three regions and identified 12 shared syllable types. The relationship between acoustic, climate, morphological, genetic distances, and the effect of geographic barrier on dialects was investigated. The results demonstrated significant acoustic variations of each syllable type among populations and regions, while the divergences were driven by diverse factors. Given that syllables are typically emitted by bats in combinations, all shared syllable types were treated as a whole and further analyzed. The results showed the acoustic distances were significantly correlated to geographical and genetic distances. Analysis through Casual Modeling revealed that geographical distance and barriers had direct influences on dialects. All populations were divided into three dialect regions, including the Northeast region, the Central-East region, and the Southwest region. Qinling Mountains served as the boundary between the Central-East region and Southwest region. This study indicated the existence of dialects in communication call of greater horseshoe bats and demonstrated the contribution of geographical factors to the formation and preservation of dialects. These results are instrumental in understanding the evolution of animal vocalizations and the processes involved in species diversity formation.