The molecular basis of high duty-cycle echolocation in bats, and its role in the divergence of populations and species

PhD thesisHow populations diverge and form new species in the face of gene flow is a key question in evolutionary biology. Recent research suggests this may be possible where the same traits affect the ecological niche and are involved in assortative mating, and that a small number of genes could be involved in driving speciation in these cases. Echolocation call frequency in bats has roles in ecology and social communication. Bats using HDC echolocation have hearing tuned to specific frequencies, with frequency shifts impacting ecological niche and mate recognition, meaning this is a good candidate trait to drive speciation. HDC echolocation has evolved independently in two highly divergent groups of bats, providing a unique opportunity to study the molecular basis of a trait potentially driving speciation. I have combined selection testing of specific loci with genomewide divergence scans to test hypotheses concerning the evolution of HDC echolocation. Members of the yangochiropteran genus Pteronotus use low duty-cycle echolocation, except for the subgenus Phyllodia. Selection tests on coding sequence data revealed loci associated with hearing under positive selection in Phyllodia and in Pteronotus, including eleven shared with a yinpterochiropteran HDC echolocator, Rhinolophus sinicus. Three size and acoustic morphs of Rhinolophus philippinensis exist in sympatry on Buton Island. Phylogenetic reconstructions revealed population structure between the morphs, though with conflicting topologies based on mitochondrial and nuclear data. Species delimitation identified at least two separate taxa. Genomewide scans of divergence indicated low background FST between the morphs, punctuated with highly diverged islands featuring an overrepresentation of genes associated with body size and hearing. 3 This thesis represents the first genome-wide investigation of HDC echolocation, highlighting candidate genes related to this trait. It additionally describes a rarely observed mammalian ecological speciation, providing support for the claim that species designated R. philippinensis represent a complex across their range