Bats’ echolocation call characteristics of cryptic Iberian Eptesicus species

Abstract

Advances in molecular methods and analyses, such as DNA sequencing and phylogenetic reconstructions, are being widely used to help clarify the taxonomic challenge posed by cryptic species. While almost morphologically indistinguishable, such species can also present other diagnostic features, including ecological and physiological characteristics. The main goal of this work was to investigate whether it is possible to distinguish two cryptic bat species in Iberia, Eptesicus serotinus and Eptesicus isabellinus, through their echolocation call characteristics. After molecular identification of species’ colonies, echolocation calls were recorded during emergence from roosts for 52 individuals. A stepwise discriminant analysis was used to test if the variables measured in the recordings could significantly differentiate the two species. This analysis was able to extract one discriminant function, with the variables’ peak frequency and duration of pulses identified as statistically significant. These provided a correct overall classification of approximately 78.8 %. We found that on average peak frequency is higher in the echolocation calls of E. isabellinus compared with that of E. serotinus, but overlap occurred between 23.4 and 28.8 kHz. Moreover, in our recording conditions, calls belonging to E. isabellinus tended to be shorter than those of E. serotinus. Possibly, some acoustic differences could be explained by local adaptations to different climate conditions and ecological niches experienced by each species.