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Short and long-term fitness consequences of maternal care in wild house mice Mus musculus domesticus


Auclair, Yannick. Short and long-term fitness consequences of maternal care in wild house mice Mus musculus domesticus. 2014, University of Zurich, Faculty of Science.

Abstract

The early life is a critical period for an individual as any developmental stress can affect its morphology, physiology, immunology or behaviour. Parental care, which consists in any parental behaviour provided to the offspring after fertilization, is thus essential in species giving birth to offspring that initially cannot thermoregulate or feed by themselves. Although a higher parental investment could improve offspring fitness, parents only have a finite quantity of energy to assign to reproduction. Decisions over energy allocation are particularly important in mammalian species where females are often the only caring parent and where lactation is the most important and costly parental care component to determine offspring development. Moreover, the long period of maternal dependence in this taxon can accentuate the importance of inter-individual variation in maternal care in the short and long term. In this thesis, I investigated the short and long-term fitness consequences of inter-individual variation in maternal care using the house mouse Mus musculus domesticus as a study species. House mice are well known for their great adaptability and are therefore a good candidate to examine inter-individual variation. Female house mice provide extensive parental care to their offspring and can be observed nesting solitarily or communally, when females pool their offspring in a single nest where they indiscriminately share all maternal duties.
An observational approach combining social, reproductive and morphological data collected from a wild population allowed me to show that females who nest communally can reduce their maternal load by spending less time in their nest without impairing the amount of maternal attention received by their offspring. Furthermore, I demonstrated that females can confuse the paternity of their litters by pooling them in communal nests which contributes to prevent infanticide and improve offspring survival. A higher maternal investment did not provide returns to females as offspring body mass at weaning failed to predict lifetime reproductive success. Moreover, higher body mass at weaning led to higher adult body mass only in males. Adult body mass, however, did not influence lifetime reproductive success but the heaviest individuals reproduced earlier and lived shorter. The studied population was subject to a strong breeding competition as reflected by the deferred onset of reproduction when population density increased and the skewed reproductive success that was observed in both sexes. Lifetime reproductive success increased with longevity. Males, who lived shorter than females, showed three alternative life history trajectories to maximize their reproductive success whereas only one was followed by females. These life history trajectories were not predicted by body mass or population density, suggesting an influence of other factors like social competence on individuals’ lifetime fitness. Finally, I used an experimental approach to test a recent theory suggesting that particular sets of behavioural traits could contribute to differences in life history traits. To do so, I assessed boldness, exploration, activity, and food consumption in laboratory-born descendants of mice caught from the study population where a survival advantage has been reported in female heterozygous for the t haplotype (+/t) over homozygous wildtype females (+/+). The longer living +/t females, unlike +/+ ones, were less active, slower to form routines and had a lower food consumption. These behavioural traits, which conserve energy and favour cautiousness, may contribute to an extended longevity.
This thesis presents new adaptive hypotheses for the evolution of communal nesting and provides empirical evidence that offspring number should be favoured over offspring quality in the house mouse. Despite a strong breeding competition in which body size plays an important role, other factors like social competence may also have a strong influence on individuals’ lifetime fitness in species living in socially complex societies like the house mouse. In line with that hypothesis, this thesis demonstrated that behavioural tendencies can correlate with a life history trait like survival. Whether or not females can tailor the behavioural profile of their offspring through the type of maternal care they provide, however, remains unknown.

Abstract

The early life is a critical period for an individual as any developmental stress can affect its morphology, physiology, immunology or behaviour. Parental care, which consists in any parental behaviour provided to the offspring after fertilization, is thus essential in species giving birth to offspring that initially cannot thermoregulate or feed by themselves. Although a higher parental investment could improve offspring fitness, parents only have a finite quantity of energy to assign to reproduction. Decisions over energy allocation are particularly important in mammalian species where females are often the only caring parent and where lactation is the most important and costly parental care component to determine offspring development. Moreover, the long period of maternal dependence in this taxon can accentuate the importance of inter-individual variation in maternal care in the short and long term. In this thesis, I investigated the short and long-term fitness consequences of inter-individual variation in maternal care using the house mouse Mus musculus domesticus as a study species. House mice are well known for their great adaptability and are therefore a good candidate to examine inter-individual variation. Female house mice provide extensive parental care to their offspring and can be observed nesting solitarily or communally, when females pool their offspring in a single nest where they indiscriminately share all maternal duties.
An observational approach combining social, reproductive and morphological data collected from a wild population allowed me to show that females who nest communally can reduce their maternal load by spending less time in their nest without impairing the amount of maternal attention received by their offspring. Furthermore, I demonstrated that females can confuse the paternity of their litters by pooling them in communal nests which contributes to prevent infanticide and improve offspring survival. A higher maternal investment did not provide returns to females as offspring body mass at weaning failed to predict lifetime reproductive success. Moreover, higher body mass at weaning led to higher adult body mass only in males. Adult body mass, however, did not influence lifetime reproductive success but the heaviest individuals reproduced earlier and lived shorter. The studied population was subject to a strong breeding competition as reflected by the deferred onset of reproduction when population density increased and the skewed reproductive success that was observed in both sexes. Lifetime reproductive success increased with longevity. Males, who lived shorter than females, showed three alternative life history trajectories to maximize their reproductive success whereas only one was followed by females. These life history trajectories were not predicted by body mass or population density, suggesting an influence of other factors like social competence on individuals’ lifetime fitness. Finally, I used an experimental approach to test a recent theory suggesting that particular sets of behavioural traits could contribute to differences in life history traits. To do so, I assessed boldness, exploration, activity, and food consumption in laboratory-born descendants of mice caught from the study population where a survival advantage has been reported in female heterozygous for the t haplotype (+/t) over homozygous wildtype females (+/+). The longer living +/t females, unlike +/+ ones, were less active, slower to form routines and had a lower food consumption. These behavioural traits, which conserve energy and favour cautiousness, may contribute to an extended longevity.
This thesis presents new adaptive hypotheses for the evolution of communal nesting and provides empirical evidence that offspring number should be favoured over offspring quality in the house mouse. Despite a strong breeding competition in which body size plays an important role, other factors like social competence may also have a strong influence on individuals’ lifetime fitness in species living in socially complex societies like the house mouse. In line with that hypothesis, this thesis demonstrated that behavioural tendencies can correlate with a life history trait like survival. Whether or not females can tailor the behavioural profile of their offspring through the type of maternal care they provide, however, remains unknown.

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Additional indexing

Item Type:Dissertation
Referees:König Barbara, Lindholm Anna K
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:July 2014
Deposited On:27 Nov 2014 08:01
Last Modified:05 Apr 2016 18:32
Funders:Swiss National Science Foundation

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