Chromosomal Variation in Certain Populations of Peromyscus boylii and Its Systematic Implications

The karyotype of Peromyscus boylii attwateri is contrasted with that of P. b. boylii, P. b. rowleyi, and P. b. utahensis. The latter three taxa have identical karyotypes. Chromosomal and morphological evidence indicate that attwateri is specifically separated from the boylii-rowleyi-utahensis assemblage. Limited samples from Mexican populations of P. boylii imply that current taxonomic alignments in this species require reevaluation. The karyotype of Peromyscus difficilis comanche is described and it appears to be identical to that of Peromyscus truei truei and unlike those of northern populations of P. difficilis.