Meeting Abstract
In mammals, social chemical cues are primarily detected by receptors in the vomeronasal organ (VNO), including proteins encoded by a large gene family known as vomeronasal type I receptors, or V1Rs. While vomerolfaction is well conserved due to its role in fitness-related behaviors, several mammalian groups have lost function, including Old World primates, some aquatic mammals, and most bats. Mammals lacking vomerolfaction are thought to exhibit a degraded VNO and pseudogenized V1Rs, but it is unclear whether these losses are related to ecology, phylogeny, or both. To investigate this question, we obtained the V1R profiles from nearly every order of mammal, and estimated the birth and death rates of gene duplication and loss. We also quantified VNO morphology from iodine-stained soft tissue µCT-scans to test how variation in vomeronasal form correlates with the evolution of V1Rs. Our results reveal that the evolutionary history of the mammalian vomerolfaction was complex, with few clear ecological explanations for loss or gain. Many mammalian orders have experienced slowed birth rates of V1R genes, but some of these lineages still possess well-developed VNOs, and retain orthologous receptors shared with distantly related species. This result suggests strong purifying selection on these genes in light of low diversification. Our study demonstrates that vomerolfaction may actually be a crucial sensory system in some species (e.g. bats) in which its function was previously underappreciated, and highlights the importance of incorporating birth-death models and phylogenetic comparative methods to understand the evolutionary history of complex traits, such as sensory systems.
