Multiple paternity in wild house mice (Mus musculus musculus): effects on offspring genetic diversity and body mass

Abstract

Multiple mating is common in many species, but it is unclear whether multiple paternity enhances offspring genetic diversity or fitness. We conducted a survey on wild house mice (Mus musculus musculus), and we found that in 73 pregnant females, 29% of litters had multiple sires, which is remarkably similar to the 23-26% found in feral populations of Mus musculus domesticus in the USA and Australia, respectively. The question is: How has selection maintained multiple mating in these subspecies since the evolutionary divergence, ca. 2800-6000 years ago? We found no evidence that multiple paternity enhanced females' litter size, contrary to the fertility assurance or genetic benefits hypotheses. Multiple paternity was associated with reduced mean and variance in offspring body mass, which suggests that females allocate fewer resources or that there is increased intrauterine conflict in multiple-versus single-sired litters. We found increased allelic diversity (though not heterozygosity) in multiple-sired litters, as predicted by the genetic diversity hypothesis. Finally, we found that the dams' heterozygosity was correlated with the mean heterozygosity of their offspring in single-and multiple-sired litters, suggesting that outbred, heterozygous females were more likely to avoid inbreeding than inbred, homozygous females. Future studies are needed to examine how increased genetic diversity of litters and smaller mean (and variance) offspring body mass associated with multiple paternity affect offspring fitness.

Keywords: Genetic benefits; genetic diversity; heterozygosity; house mice; multiple paternity.

Figure 1

Male and female house mouse (Mus musculus musculus).

Figure 2

(A) Litter size of single-and multiple-sired litters and (B) mean weanling body mass (g) within single-and multiple-sired litters.

Figure 3

(A) Offspring mean observed heterozygosity of single-versus multiple-sired litters. (B) Offspring mean observed heterozygosity in the KLIVV and Safari park populations.

Figure 4

Offspring mean observed heterozygosity in litters born in winter, spring or summer. Circles refer to outliers.

Figure 5

(A) Offspring mean number of alleles within single-and multiple-sired litters. (B) Offspring mean number of alleles within litters from the KLIVV or Safari park population.

Figure 6

Correlation between dams' observed heterozygosity and offspring mean heterozygosity for single (white, dashed line R² = 0.27)-and multiple (black, solid line, R² = 0.29)-sired litters.