Genetic variation and correlations between genotype and locomotor physiology in outbred laboratory house mice (Mus domesticus)

Laboratory strains of house mice (Mus domesticus) are increasingly used as model organisms in evolutionary physiology, so information on levels of gen etic variation is important. For example, are levels of genetic variation c omparable to those found in populations of wild house mice? We studied allo zymes to estimate genetic variation in outbred Hsd:ICR mice, which have bee n used in several studies with evolutionary emphasis. The physiological sig nificance of allozyme Variation remains obscure. Several workers have repor ted relationships between multi-locus heterozygosity and metabolic traits, but endotherms have not been studied. Therefore, we also measured mice for basal metabolic rate (BMR), maximal oxygen consumption during forced treadm ill exercise (V) over dot O(2)max), and 12 other traits related to locomoto r physiology, before genotyping them for 10 allozyme loci. Four of these lo ci were polymorphic, all were in Hardy-Weinberg equilibrium, and inbreeding coefficients were not significantly different from zero. Average heterozyg osities were 11%, similar to values reported for wild populations of house mice. Fourteen percent of the associations between single-locus genotype an d physiological traits were statistically significant. Multi-locus heterozy gosity was not significantly related to (V) over dot O(2)max), but was posi tively correlated with BMR, a result opposite to the negative correlation b etween standard metabolic rate and heterozygosity reported in many ectother ms. Therefore, the proposed mechanisms for the effect of multi-locus hetero zygosity on metabolic rate in ectotherms may not apply to endotherms. (C) 1 999 Elsevier Science Inc. All rights reserved.