Ecologic and Genetic Variability within Species of Peromyscus

Within every wide-ranging subspecies of animal there is a considerable amount of local variability, at least a considerable part of which is based on hereditary differences. The pelage color of Peromyscus and other small mammals tends to match the color of the surface soil of the habitat, demonstrating a control by the environment of part of the heredity of these animals. There also is evidence that some subspecies of Peromyscus have had a polyphyletic origin. Accordingly, the subspecies is considered to be primarily an ecologic unit, rather than a unit of similar descent or of similar heredity.