MITOCHONDRIAL DNA AND PROTEIN DIFFERENTIATION BETWEEN HYBRIDIZING CYTOTYPES OF THE WHITE-FOOTED MOUSE, PEROMYSCUS LEUCOPUS.

Restriction-enzyme analysis of mitochondrial DNA and protein electrophoresis were used to document patterns of gene flow across a hybrid zone between chromosomal races of Peromyscus leucopus. Chromosomal markers (three inversions) are such that individuals can be classified as potential F 's, backcrosses, or parental types. Allozymic characterization of the hybrid zone is congruent with the chromosomal data (Stangl, 1986) and indicates an assymetrical distribution of markers, with the northeastern markers being distributed at a higher frequency into southwestern populations. Restriction patterns of mtDNA suggest that the two cytotypes may have had different evolutionary histories, and the distribution of haplotypes is concordant with other genetic markers used to identify the hybrid zone. Concordant changes in chromosomes, allozymes, and mtDNA suggest that the most viable hypothesis for the origin of the zone is secondary contact. A unique aspect of this study is that the same individuals were used for protein electrophoresis, mtDNA analysis, and chromosomal analysis. Thus, patterns of genetic variation can be interpreted free of any historical bias associated with samples collected at different times.