Welcome to the Year of the Rat! In Chinese culture, rats are a sign of wealth and abundance and similarly, rodents are the most abundant and species rich order of mammals, representing 40% of all extant mammals. Shockingly, there are comparatively few rodent genomes available relative to larger, more charismatic mega-fauna like cats and dogs.
We are excited to launch 2020 and the Year of the Rat with the release of the Northern rock mouse Peromyscus nasutus (Allen 1981) genome assembly, adding to a much-needed repertoire of rodent genomes that can now be used in human biomedical research and comparative genomics. The Criceidae family of rodents, to which P. nasutus belongs, includes almost 600 species of true hamsters, voles, lemmings, and New World rats and mice – the second-largest family of mammals.
Peromyscus nasutus has a long and slender nose relative to other Peromyscus species, but it would be otherwise hard to distinguish if not for its 'nosey' appearance (nasus means 'nose' in Latin). As the common name suggests, the northern rock mouse loves rocks and doesn't live too far from rocky areas in the Southern United States (mostly Colorado and New Mexico) and Mexico. The information contained in its scientific and common names, pointing to a long-nosed rock-loving mouse, is pretty much all we know about this species, starting from 'is this a species'?
In fact, the taxonomy of the Northern rock mouse has been subject of debate for decades. Previously recognized as a subspecies of Peromyscus difficilis, genetic inquiry has recently elevated it to the full-species level and this new assembly expands opportunities for further systematic inquiry. Will P. nasatus continue to be recognized as a species, or will it be demoted to just a population of Peromyscus difficilis, a closely related species?
The tissue sample was loaned to the MacManes lab by the Museum of Southwestern Biology, as part of a larger study on how desert mammals survive intense heat and drought. It was collected in 2017 in El Malpais National Conservation Area, Cibola County, New Mexico, USA by Kayce Bell and colleagues. The full collection record can be found at http://arctos.database.museum/guid/MSB:Mamm:299083.