Diversity in olfactory receptor repertoires is associated with dietary specialization in a genus of frugivorous bat

Mammalian olfactory receptors (ORs) are a diverse family of genes encoding proteins that directly interact with environmental chemical cues. ORs evolve via gene duplication in a birth-death fashion, neofunctionalizing and pseudogenizing over time. Olfaction is a primary sense used for food detection in plant-visiting bats, but the relationship between dietary specialization and OR repertoires is unclear. Within neotropical Leaf-nosed bats (Phyllostomidae), many lineages are plant specialists, and some have a distinct OR repertoire compared to insectivorous species. Yet, whether specialization on particular plant genera is associated with the evolution of more specialized OR repertoires has never been tested. Using targeted sequence capture, we sequenced the OR repertoires of three sympatric species of short-tailed leaf-nosed bats (*Carollia*), which vary in their degree of specialization on the fruits of *Piper* plants. We characterized orthologous versus duplicated receptors among *Carollia* species, and identified orthologous receptors and associated paralogs to explore the diversity and redundancy of the receptor gene repertoire. The most dedicated *Piper* specialist, *Carollia castanea*, had lower OR diversity compared to the two more generalist species (*sowelli*, *perspicillata*), but we discovered a few unique sets of ORs within *C. castanea* with exceptional redundancy of similar gene duplicates. These unique receptors potentially enable *C. castanea* to detect *Piper* fruit odorants to an extent that the other species cannot. *C. perspicillata*, the species with the most generalist diet, had a larger diversity of functional receptors, suggesting the ability to detect a wider range of odorant molecules. The variation among ORs may be a factor in the coexistence of these sympatric species, facilitating the exploitation of different plant resources. Our study sheds light on how gene duplication plays a role in dietary adaptations and underlies patterns of ecological interactions between bats and plants.