Geographical variation in echolocation vocalizations of the Himalayan leaf‐nosed bat: contribution of morphological variation and cultural drift

Abstract

Ecologists and evolutionary biologists have a long-standing interest in the patterns and causes of geographical variation in animals ' acoustic signals. Nonetheless, the processes driving acoustic divergence are still poorly understood. Here, we studied the geographical variation in echolocation vocalizations (commonly referred to as echolocation ' pulses ' given their short duration and relatively stereotypic nature, and to contrast them from the communicative vocalizations or ' calls ' ) of a widespread bat species Hipposideros armiger in south China, and assessed whether the acoustic divergence was driven by either ecological selection, or cultural or genetic drift. Our results revealed that the peak frequency of echolocation pulses varied signifi cantly across populations sampled, with the maximum variation of about 6 kHz. Th e peak frequency clustered into three groups: eastern and western China, Hainan and southern Yunnan. Th e population diff erences in echolocation pulses were not signifi cantly related to the variation in climatic (mean annual temperature, mean annual relative humidity, and mean annual precipitable water) or genetic (genetic distance) factors, but signifi cantly related to morphological (forearm length) variation which was correlated with mean annual temperature. Moreover, the acoustic diff erences were signifi cantly correlated with geographical and latitudinal distance after controlling for ' morphological distance ' . Th us, neither direct ecological selection nor genetic drift contributed to the acoustic divergence observed in H. armiger . Instead, we propose that the action of both indirect ecological selection (i.e. selection on body size) as well as cultural drift promote, in part, divergence in echolocation vocalizations of individuals within geographically distributed populations.

Geographical variation in the high-duty cycle echolocation of the cryptic common mustached batPteronotuscf.rubiginosus(Mormoopidae)

“…In contrast to what has been found in birds, where genetic discontinuities are due to dialect 351 boundaries (Slabbekoorn and Smith 2002), acoustic divergence within bat species is unlikely to be small morphological differences in the vocal apparatus, or even in body size, could also be 358 responsible for producing different frequencies (Lin et al 2014). For instance, it has been shown 359 that a larger larynx produces lower frequencies than a smaller one (Jones 1999).…”

“…However, it is still unclear whether it is the 50 cause or the consequence of a reduction in levels of gene flow within the species (Jiang et al 51 2013). Although it has been shown that at different geographical scales this sensory divergence 52 may emerge as a result of either direct ecological selection, genetic drift, cultural drift or indirect 53 ecological selection , Keighley et al 2017, Lin et al 2014, our understanding of 54 it is still far from complete ).…”

“…However, due to the relatively small difference in FME between the 302 sympatric populations of these two lineages of Pteronotus it seems unlikely that these differences 303 are related to prey size. Jiang et al (2013) and Lin et al (2014) suggested that variations of 5-7 304 kHz in FME do not impact prey detection ability and thus, might not directly affect resource use.…”

Parallel evolutionary forces influence the evolution of male and female songs in a tropical songbird

“…Our results support greater roles for both acoustic adaptation and cultural isolation on acoustic divergence than neutral genetic divergence in both sexes. Acoustic patterns were correlated with genetic distance, but acoustic changes appeared to occur independently of genetic changes, suggesting that cultural drift and cultural selection have a stronger influence on the evolution of acoustic signals than neutral genetic divergence (Wright et al ., ; Byers et al ., ; Lin et al ., ; Potvin & Clegg, ). With respect to the acoustic adaptation hypothesis, ambient noise differences rather than habitat differences between populations had a greater effect on acoustic divergence.…”

The effects of cultural drift on geographic variation in echolocation calls of the Chinese rufous horseshoe bat (Rhinolophus sinicus)

“…Second, geographic variations in call characters are largely related to geographic factors such as distance between capture locations (geographic distance), latitude, and/or longitude (Chen et al., ; Jang et al., ; Lin et al., ; Sun et al., ; Yoshino et al., ). The cultural drift hypothesis predicts a positive correlation between acoustic and geographic distance because learned vocal signals between populations may have diverged stochastically via cultural transmission or social learning and copying errors.…”