Social call divergence in bats: a comparative analysis

Acoustic signals mediate important life history events in a variety of species, providing new vistas for understanding speciation. It has been proposed that animal acoustic signals undergo complex interactions among morphology, ecology, social pressure, and phylogenetic history. Yet, the relative importance of these factors in shaping acoustic divergence is rarely assessed within a comparative framework. Herein, we aim to investigate the key determinants of social call divergence across 31 bat species from 5 families. We compiled a wide data set on bat aggressive calls, body size, foraging habitats, foraging modes, climatic conditions, colony size, and phylogenetic components. We identified remarkable interspecific divergence versus within-species variation in aggressive vocalizations. Despite weak effects of ecological factors, colony size, body size, and phylogenetic components accounted for the majority of variation in call parameters among species. The colony size and body size played a major role in influencing spectral parameters, whereas phylogenetic relationships determined call duration and minimum frequency. Together, our findings constitute convincing evidence that sociality, morphological constraint, and phylogenetic constraint mold social call divergence in bats. This study expands our limited knowledge of the evolution of bat social calls, and highlights the importance of sociality in driving acoustic phenotype diversity.