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Atmospheric humidity affects global variation of bat echolocation via indirect effects

  • Kotila, Miika1
  • Helle, Samuli2
  • Lehto, Harry J.3
  • Rojas, Danny4
  • Vesterinen, Eero J.5, 6
  • Lilley, Thomas M.7
  • 1 Biodiversity Unit, University of Turku, Turku , (Finland)
  • 2 Department of Social Research, University of Turku, Turku , (Finland)
  • 3 Department of Physics and Astronomy, University of Turku, Turku , (Finland)
  • 4 Department of Natural Sciences and Mathematics, Pontificia Universidad Javeriana Cali, Cali , (Colombia)
  • 5 Department of Biology, University of Turku, Turku , (Finland)
  • 6 Department of Ecology, Swedish University of Agricultural Sciences, Uppsala , (Sweden)
  • 7 Finnish Museum of Natural History, University of Helsinki, Helsinki , (Finland)
Published Article
Frontiers in Ecology and Evolution
Frontiers Media SA
Publication Date
Sep 06, 2022
DOI: 10.3389/fevo.2022.934876
  • Ecology and Evolution
  • Original Research


The peak frequency of bat echolocation is a species-specific functional trait linked to foraging ecology. It is tailored via evolution to suit conditions within the distribution range of each species, but the evolutionary drivers are not yet well-understood. Global patterns of humidity correlate with many aspects of bat ecology. We hypothesized that atmospheric absolute humidity could explain global peak frequency variation directly and indirectly via increasing species body size and bat species richness. These hypotheses were tested using Bayesian phylogenetic path analysis on 226 tropical and subtropical bat species. In line with our predictions, we found a positive total effect of humidity on peak frequency, which was dominated by the positive indirect effects via body size and bat species richness. We did not observe the negative direct effect of humidity on peak frequency, which was hypothesized based on atmospheric attenuation of sound. In line with our expectations, excluding the predominantly clutter foraging bat families from our dataset downplayed the importance of the richness-mediated route. To conclude, our findings suggest that indirect effects, owing to ecology and biogeography of bat taxa, play a major role in the global relationship between peak frequency and atmospheric humidity.

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