Biochemical and Karyotypic Variation in Peromyscus maniculatus from Western North America

Abstract

Standard karyotypic and biochemical variation was examined for 13 populations, referable to four subspecies of Peromyscus maniculatus from western United States and Baja California, Mexico. Fundamental number variation among individuals included a range of 72 to 82, and ranges for the subspecies overlapped broadly. Although genic variation was substantial (P̄ = 20.2%, H̄ = 0.053), estimates of fixation indices (F̄ST) indicated only moderate genetic differentiation of populations. The calculated average number of migrants exchanged between local populations (Nmest = 3.73) suggests that moderate to high levels of gene flow are maintained. Coefficients of genetic similarity (S̄ = 0.973) and identity (Ī = 0.995) were among the highest reported for local populations of Peromyscus. Phenetic analysis of the biochemical data failed to indicate clustering of populations on the basis of subspecific affiliation. Overlapping ranges of FN and high levels of biochemical similarity are attributed to gene flow among the populations. Morphological distinctions of the subspecies are attributed to environmental adaptations, operating within this background of genetic interchange.