Data and code from: Dialect formation in ghost bats: Genetic, geographic, and morphological drivers of social and echolocation call divergence

Geographical patterns of vocal dialects are poorly understood in bats,
despite growing evidence that they possess complex vocal communication
systems. We investigated patterns and drivers of variation in
vocalisations recorded at five ghost bat colonies in the Northern
Territory, Australia. We calculated the genetic and morphological
distances among individuals and investigated correlations with geographic
distance. We then determined variation within three ghost bat social
vocalisations (“Chirp-trill”, “Squabble”, “Ultrasonic Social”) and their
“Echolocation” call using seven spectrographic measurements. Finally, we
tested whether acoustic distance could be explained by genetic,
geographic, or morphological distance. Geographic and genetic distance
were highly correlated, suggesting the occurrence of isolation by
distance. All measures of morphological distance were consistent with
Bergmann’s Rule, except noseleaf shape, which is likely constrained by its
role in echolocation. Geographic variation was evident within each of the
three social vocalisations and the echolocation call, with the patterns of
geographic variation differing among the four vocalisation types. The
degree of difference was surprising, given the ghost bat’s long-range
seasonal dispersal. Acoustic distance in Chirp-trill and Squabble calls
was marginally significantly correlated with genetic (and geographic)
distance. In contrast, Ultrasonic Social and Echolocation calls varied
among colonies but showed no significant associations with other metrics,
apart from a weak correlation between Ultrasonic Social distance and
forearm length. This supports the view that these ultrasonic calls are
under stabilising selection due to their role in foraging and orientation.
This study provides the first evidence of dialect formation in
megadermatid bats. It highlights the importance of considering multiple
vocalisation types and investigating multiple processes in signal
evolution. Overall, we found genetic, geographic, and morphological
distances accounted for some of the variation in acoustic differences
among colonies, but further work is needed to investigate other processes
that may also contribute to dialect formation in ghost bats.