Biochemical Variation and Systematics of Peromyscus pectoralis

The genetic structure of 21 populations of P. pectoralis has been analyzed through electrophoretically demonstrable variation in proteins encoded by 17 to 21 structural loci. A wide range in levels of heterozygosity, 0.0 to 0.178, with a mean of 0.05, and levels of genetic similarity, 0.691 to 0.991, with a mean of 0.829, were exhibited among populations of P. pectoralis . This variation in levels of heterozygosity and genetic similarity is thought to be the result of colonization and, hence, genetic contribution from populations from three Pleistocene refugia with differentiated gene pools. With the removal of the primary isolation barriers, gene exchange between populations derived from different refugia have produced populations with high levels of heterozygosity. Because individual populations of P. pectoralis have received their genetic makeup from one to three different gene pools, they exhibit lower levels of genetic similarity than observed among most conspecific populations of this genus.