Phylogeny, Genes, and Hearing: Implications for the Evolution of Echolocation in Bats

Abstract

Bats are arguably the most unusual of mammals, uniquely able to fly and also distinctively capable of laryngeal echolocation, enabling them to orient and move in complete darkness. The evolution of echolocation has fascinated and intrigued scientists for decades and has stimulated many phylogenetic studies to resolve the evolutionary history of bats and laryngeal echolocation. In this chapter, the consensus and conflict regarding bat evolutionary relationships is explored based on key phylogenetic studies conducted over the past 15 years. The consequential conclusions regarding the evolution of bats' unique sensory perception are detailed. Using these consensus phylogenies as an evolutionary framework, the search for the genomic signatures of echolocation is described, and the spectacular unprecedented sequence convergence observed between echolocating bats and whales is highlighted. What is currently known about the molecular basis of echolocation is detailed and the future steps required to link this trait with its genomic bases are explored. It is often argued that the evolution of one specialization will have consequences for other traits, and, in the case of echolocation, a ``trade-off'' between the senses must occur. In this chapter, the potential molecular sensory trade-offs between echolocation, vision, olfaction, and taste are explored. Finally, the next steps required to ultimately reach a universal consensus regarding bat phylogenetic relationships are discussed together with future directions for elucidating the genomic basis of echolocation in mammals and the extent of molecular ``trade-offs'' that occur in these unique species.