The major histocompatibility complex and mating preferences in wild house mice (Mus domesticus)

This study examined the relationship between the major histocompatibility complex (MHG) genes and mate choice by wild house mice in a controlled laboratory setting in an attempt to understand the mechanisms maintaining natural MHC diversity. Three rearing groups of wild test mice were produced: nonfostered control mice, mice fostered into families of an inbred laboratory mouse strain, and mice fostered into families of a second mouse strain differing genetically from the first only within the MHC region. At maturity test mice were given a choice of two opposite-sex stimulus mice of the two MHC-congenic strains used for fostering. Test mice were scored for several measures of preference including amount of time spent with either stimulus mouse, and ejaculation with a stimulus mouse. Females in mio of three rearing groups spent more time with one MHC type regardless of rearing environment, suggesting that females did not prefer mates dissimilar from family MHC type. Time preferences tended to he: stronger in females than in males. Male test mice ejaculated indiscriminately. Female wild mice mated to ejaculation more often in longer trials, but these matings were still too infrequent to assess preferences. Fostering had little or no effect on MHC-based mate preferences of wild house mice, and no evidence suggested that MHC was used to avoid inbreeding. Wild female mice may still choose mates based on MHC haplotypes (but do not necessarily prefer MHC-dissimilar mates); other cues are probably also used. Based on these results, inbreeding avoidance does not seem a strong mechanism for maintaining natural MHC diversity.