Karyotypes of Eight Species of Mexican Rodents (Muridae)

Karyotypes of six species of murid rodents from Mexico are reported for the first time, including: Nyctomys sumichrasti, Peromyscus hylocetes, Peromyscus perfulvus, Peromyscus banderanus, Baiomys musculus , and Neotoma goldmani . The chromosomes of some species clearly suggest affinities within the appropriate taxa. Identity of the sex chromosomes and an apparent automosomal polymorphism are shown for Neotoma alleni . The karyotype of Microtus mexicanus from western Mexico is polymorphic for two pairs of chromosomes and, more importantly, differs significantly from that of presumed M. mexicanus occurring north of Mexico.