The sonar beam of Macrophyllum macrophyllum implies ecological adaptation under phylogenetic constraint

All animals are adapted to their ecology within the bounds of their evolutionary heritage. Echolocating bats clearly show such adaptations and boundaries through their biosonar call design. Adaptations include not only the overall time-frequency structure, but also the shape of the emitted echolocation beam. Macrophyllum macrophyllum is unique within the phyllostomid family, being the only species to predominantly hunt for insects in the open, on or above water, and as such it presents an interesting case for comparing the impact of phylogeny and ecology as it originates from a family of low-intensity, high-directionality gleaning bats, but occupies a niche dominated by very loud and substantially less-directional bats. Here, we examined the sonar beam pattern of M. macrophyllum in the field and in a flight room and compared it to closely related species with very different feeding ecology and to that of the niche-sharing but distantly related Myotis daubentonii Our results show that M. macrophyllum uses higher source levels and emits less-directional calls than other phyllostomids. In the field, its call directionality is comparable to M. daubentonii, but in the flight room, M. macrophyllum is substantially more directional. Hence our results indicate that ecology influences the emitted call, pushing the bats to emit a louder and broader beam than other phyllostomids, but that phylogeny does limit the emitted intensity and flexibility of the overall beam pattern.