Variation in the genetic structure of Peromyscus populations. I. Genetic heterozygosity--its relationship to adaptive divergence.

The genetic structure of nine Peromyscus maniculatus nebrascensis demes from southeastern Wyoming was determined by analyzing allozymes encoded by 23 genetic loci with polyacrylamide gel electrophoresis. Genetic variability is extremely high for two genetic parameters; the proportion of loci polymorphic per deme averaged 0.41. Previous estimates of genetic heterozygosity for species within the genus Peromyscus have a mean of 0.06. The results of the present study suggest that genetic heterozygosity is considerably higher within P. maniculatus demes than within demes of other species in the genus. Geographic range is correlated with heterozygosity among Peromyscus species, as is adaptive divergence into broad-niched species. These correlates suggest that high heterozygosity may reflect an adaptation to a variable environment.