Geographic variation and discrimination of social calls in male great himalayan leaf-nosed bats: do functionally similar calls have similar patterns?

Geographical variation in animals’ acoustic signals has received much attention. However, few studies have compared the patterns and underlying selective forces driving geographical divergence of vocalizations with similar and different functions within the same species. Also, the social consequences of geographical divergence in acoustic signals are still rather poorly understood. Here we recorded three types of social calls of male great Himalayan leaf-nosed bats (Hipposideros armiger) across eight colonies in China. Two calls share similar functions and the third has a function distinct from the other two. We examined the patterns and causes of geographical variation of each of these calls. We found that all three calls had significant geographic variation with similar patterns of spatial variation. Only one of the two social calls with similar functions was found to be affected by genetic drift, while the other two calls were not affected by selection, drift, or morphological constraints. Furthermore, we found that bats could discriminate between vocalizations of their own colony and those of an allopatric colony. Overall, these results suggest that acoustic signals with similar functions may be shaped by different driving forces and acoustic signals with different functions may exhibit similar geographical patterns. This study expands our limited knowledge of the patterns of geographical variation of vocalizations emitted at different emotional states and highlights the importance of comparing simultaneously patterns and causes of geographical divergence of vocalizations with similar and different functions. This study provides the empirical evidence suggesting that calls with a similar function may fail to co-vary and alternatively calls with a different function may co-vary. Moreover, we show that bats can discriminate between calls of their own colony from those of a foreign colony. These results expand our limited knowledge of the patterns of geographical variation of vocalizations uttered under different emotional states and the nature of functional drivers that influence the evolution of communicative systems.