Dominance and reproductive behavior of wild house mice in a seminatural environment correlated with T-locus genotype

Summary Behavior of mice whose T-locus genotype was either +/+ or +/t was observed in a seminatural environment. Heterozygous females were less likely to be dominant, less likely to go into behavioral estrus, and less likely to become pregnant than were +/+ females. The relative fitness of +/t as compared with +/+ females was 0.32:1.00. In contrast, +/t males produced 35% more young than did +/+ males. The higher fitness of +/t males was primarily due to a greater production of young on the part of +/t as compared with +/+ subordinate males. Little evidence was found under these naturalistic conditions, of non-random mating with respect to T-locus genotype. The indication of overdominance for +/t males makes it unlikely that heterozygote disadvantage will be sufficient to account for the frequency of t-alleles in natural populations.