Molecular phylogenetics and the evolution of high-frequency echolocation in horseshoe bats (Genus Rhinolophus)

Abstract

Horseshoe bats (genus Rhinolophus) belong to the Old World family Rhinolophidae. They are high-duty cycle bats and many species use echolocation calls dominated by high frequencies (above 60 kHz). Much is known about how they use their echolocation calls, but very little is known about why these bats use echolocation calls of such high frequencies, or what has caused the divergence in echolocation call frequency between rhinolophid species. I test five hypotheses that may explain the evolution and divergence of high frequencies in the horseshoe bats: (1) The Allotonic Frequency Hypothesis - echolocation frequencies outside of moth hearing range (allotonic frequencies) have evolved in response to moth hearing; (2) The Allometry Hypothesis - highfrequency echolocation calls are simply a function of body size; (3) The Acoustic Adaptation Hypothesis - selection pressures linked to habitat structure have shaped the evolution of high-frequency echolocation calls; (4) The Foraging Habitat Hypothesis - foraging style and habitat of a bat should correspond to echolocation call frequency and wing design; and (5) The Acoustic Communication Hypothesis - echolocation frequencies evolved under selection pressure which eliminated overlap among sympatric species of rhinolophids, within the context of effective communication.