Taxonomic assessment of two wild house mouse subspecies using whole-genome sequencing

Abstract

House mice (Mus musculus) are comprised of three primary subspecies. A large number of secondary subspecies have also been suggested on the basis of divergent morphology and molecular variation at limited numbers of markers. While the phylogenetic relationships among the primary M. musculus subspecies are well-defined, the relationships among the secondary subspecies, and their relationships to primary subspecies, remain poorly understood. Here, we integrate de novo genome sequencing of museum-stored specimens of house mice from one secondary subspecies (M. m. bactrianus) and publicly available genome sequences of house mice previously characterized as M. m. helgolandicus, with whole-genome sequences from diverse representatives of the three primary house mouse subspecies. We show that mice assigned to the secondary M. m. bactrianus and M. m. helgolandicus subspecies are not genetically differentiated from the contemporary M. m. castaneus and M. m. domesticus, respectively. Overall, our work suggests that the M. m. bactrianus and M. m. helgolandicus subspecies are not well-justified taxonomic entities, emphasizing the importance of leveraging whole-genome sequence data to inform subspecies designations. Additionally, our investigation has established experimental procedures for generating whole-genome sequences from air-dried museum specimens and provides key genomic resources to inform future genomic investigations of wild mouse diversity.