Abstract
In mammals, reproduction is influenced by sexual competition, temperature and food availability and these factors might be crucial already during early life. Favorable early life environment and high maternal investment are expected to improve survival and reproduction. For example, in mammals, maternal investment via lactation predicts offspring growth. As body mass is often associated with fitness consequences, females have the potential to influence offspring fitness through their level of investment, which might interact with effects of population density and temperature. Here, we investigate the relationship between house mouse (Mus musculus domesticus) pup body mass at day 13 (used as approximation for weaning mass) and individual reproductive parameters, as well as longevity, under natural variation in population density and temperature (as approximation for season). Further, we assessed the extent to which mothers influence the body mass of their offspring until weaning. To do so, we analyzed life data of 384 house mice from a free-living wild commensal population that was not food limited. The mother’s contribution accounted for 49% of the variance in pup body mass. Further, we found a complex effect of population density, temperature and maternal investment on life-history traits related to fitness: shorter longevity with increasing pup body mass at day 13, delayed first reproduction of heavier pups when raised at warmer temperatures, and increased lifetime reproductive success for heavier pups at high densities. Our study shows that the effects of maternal investment are not independent of the effects of the environment. It thus highlights the importance of considering ecological conditions in combination with maternal effects to unravel the complexity of pup body mass on fitness measures.
Highlights
Organisms adopt different life-history strategies to cope with changing environments, trading off growth, survival and reproduction
Previous laboratory studies have shown that maternal investment through lactation can explain up to 65% of the variation observed in body mass at weaning in the house mouse Mus musculus (Cox et al, 1959; El Oksh et al, 1967; Atchley and Zhu, 1997)
Individual lifetime reproductive success (LRS, measured by the number of offspring surviving until day 13 over a lifetime) was influenced by the interaction of pup body mass at day 13 with population density at birth (Figure 3 and Table 1)
Summary
Organisms adopt different life-history strategies to cope with changing environments, trading off growth, survival and reproduction. Previous laboratory studies have shown that maternal investment through lactation can explain up to 65% of the variation observed in body mass at weaning in the house mouse Mus musculus (Cox et al, 1959; El Oksh et al, 1967; Atchley and Zhu, 1997). This maternal source of variance in offspring phenotype can be partitioned into prenatal maternal effects like resources allocated to an egg, and postnatal maternal effects such as maternal behavior. In species with a prolonged period of maternal dependence, the contribution of postnatal maternal effects on offspring body size can outweigh the effects of prenatal maternal effects (Reinhold, 2002; Steiger, 2013)
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