The vomeronasalorgan(VNO) plays a key role in sensing pheromonal cues, whichelicits social and reproductive behaviors. Although
the VNO is highly conserved across mammals, it has been lost in some species that have evolved alternate sensing systems during
diversification. In this study, we investigate a newly identified VNO-specific gene, ancV1R, in the extant 261 species of mammals to
examine the correlation between genotype (ancV1R) and phenotype (VNO). As a result, we found signatures for the relaxation of
purifying selection (inactivating mutations and the elevation of dN/dS) on ancV1Rs in VNO-lacking mammals, such as catarrhine
primates, cetaceans, the manatees, and several bat lineages, showing the distinct correlation between genotype and phenotype.
Interestingly,we furtherrevealedsignaturesforthe relaxationof purifying selectionon ancV1R intrue seals, otters, thefossa, the owl
monkey,andalcelaphineantelopesinwhichtheexistenceofafunctionalVNOisstillunderdebate.OuradditionalanalysesonTRPC2,
another predictive marker gene for the functional VNO, showed a relaxation of purifying selection, supporting the possibility of VNO
loss in these species. The results of our present study invite more in-depth neuroanatomical investigation in mammals for which VNO
function remains equivocal.
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