Genetic Variation in Island and Mainland Populations of Peromyscus Leucopus

Protein variation controlled by 28 genetic loci was analyzed in samples from three island and three mainland populations of the white-footed mouse, Peromyscus leucopus. Nine of the 28 loci have polymorphic al?eles in one or more of the populations. Island populations were less variable genetically than mainland popu- lations. Estimated heterozygosity (H) had a mean value of 7.1% for island populations and 8.0% for mainland populations. The proportion of loci polymorphic (P) for island and mainland populations corre- sponded to 21.4 and 32.1%, respectively. Coefficients of genetic simi- larity (S) for paired geographical populations ranged from 0.92 to 0.99.