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Genetic and Social Structure of Feral House Mouse Populations on Grizzly Island, California

Myers, Judith H.
Ecology 1974 v.55 no.4 pp. 747-759
Mus musculus, environmental factors, esterases, farm buildings, females, feral animals, gene frequency, genotype, grasslands, hemoglobin, loci, mice, reproduction, sexual maturity, social structure, trapping, California
Two populations of house mice living in open grassland in northern California were tested for demic structure, which has been reported for populations living in farm buildings. Mice captured in each of two 0.8—ha trapping areas were typed for two blood proteins (hemoglobin and an esterase). Nonrandom distributions of genotypes within the populations occasionally occurred, but were not temporally stable. During part of the study, allele frequencies at the hemoglobin locus were significantly different in the two populations. An analysis of selection showed that differential survival and reproduction favored different genotypes in each population. Numbers of mice fluctuated dramatically on the two areas, reflecting the variability of conditions to which feral mice are exposed. A period of colonization occurred in one of the trapping areas, and young females that became sexually mature just before or immediately after their movement to this area were prevalent among the colonizing mice. Dispersal, caused by fluctuating environmental conditions, appears to be an important aspect of feral house mouse population structure, and feral populations are not divided into temporally stable, closed genetic units as are populations living in farm buildings.