Evolution of V1R Repertoires in Subterranean Rodents

Abstract

Pheromones are chemicals released and perceived by members of the same species, triggering sexual and social behaviours or physiological changes in diverse animals. Although rodents are the first mammals in which vomeronasal receptors and their major roles in pheromonal olfaction were identified, little is known about the evolution of vomeronasal receptor gene repertoires in subterranean rodents. Recent genome‐wide surveys in rodents have shown that the number of functional vomeronasal type 1 receptor ( V1R ) genes was markedly reduced in phylogenetically distinct subterranean rodents compared with their superterranean relatives, possibly due to confined pheromonal signals in underground burrows. Interestingly, population genetic analysis proved that many V1R genes may have undergone positive selection rather than relaxed selection in one species of subterranean rodent. Exploration of functional roles of the reduced number of V1R genes would help to uncover the importance of pheromonal olfaction in subterranean rodents. Key Concepts Pheromones are odour molecules that elicit sexual and social behaviours or physiological changes in conspecific individuals. Subterranean rodents live in underground burrows with confined pheromonal signals, which represent a contrasting lifestyle compared with their superterranean relatives. Genome‐wide surveys have shown that convergent reduction in vomeronasal type 1 receptor (V1R) repertoires in multiple lineages of subterranean rodents was significantly associated with their lifestyle. Population genetic analysis revealed that many V1R genes may have undergone positive selection rather than relaxed selection in one species of subterranean rodent. Our understanding of the importance of pheromonal olfaction and its receptor genes appears to be incomplete in animals.

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“…While V1Rs are mainly involved in detecting air-borne molecules scattered in the air, V2Rs are commonly responsible for binding to water-soluble peptides abundant in aquatic environments ( Shi and Zhang, 2007 ). Recently, it was shown that there has been a convergent reduction of V1Rs in different subterranean rodents, including the BMR ( Jiao et al, 2019 ; Zhao, 2021 ), suggesting that pheromonal olfaction mediated by V1Rs might be reduced, as it may not be as useful as seismic communication in the underground tunnel environment.…”