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Maternal effects in birds: effects of nutritional conditions on maternal reproductive effort and offspring performance


Giordano, Marta. Maternal effects in birds: effects of nutritional conditions on maternal reproductive effort and offspring performance. 2014, University of Zurich, Faculty of Science.

Abstract

The environment experienced by an organism at different life stages can have substantial effects on its phenotype. The environmental conditions the mother encounters can substantially influence her investment in the present reproductive attempt, and the phenotype of her offspring through the so-called maternal effects. Moreover, prenatal and early postnatal conditions experienced by offspring can interact and modulate their life histories. The aim of this thesis is to give new insight into environmentally induced maternal effects and to test the effects of the interaction between pre- and early postnatal conditions on offspring physiology and morphology in a wild-living bird species, the great tit (Parus major). In Chapter one, I investigated how an environmental match / mismatch between the food availability encountered by mothers during egg laying (i.e. prenatal environment) and by nestlings during early growth affected the developmental trajectories of nestlings, testing for a possible role of yolk androgens in mediating potential prenatal maternal effects. I found no evidence that nestlings performed better when experiencing matching nutritional conditions. However, being raised in the original nest by the biological parents (i.e. matching conditions) had positive effects on nestling growth and body mass. I was able to show significant interactive effects of pre- and postnatal food availability on nestling body growth, and significant effects of maternal food availability on nestling body size and mass. However, these effects were not mediated by yolk androgen deposition. The results of this experiment suggest that food-induced maternal effects can have substantial effects on fitness-related traits of the offspring by influencing their efficiency to use nutritional resources. They also highlight the necessity to take multiple environmental factors into account when studying the effects of environmental match / mismatch on offspring phenotype. In Chapter two I assessed how pre- and early postnatal nutritional conditions and their match / mismatch can affect the physiological conditions, measured as oxidative status, of male and female nestling great tits. My findings revealed that the nutritional conditions experienced by mothers and by offspring during growth affect the physiological condition of nestlings in a sex-specific way. Female nestlings whose mother has not been food-supplemented, and female nestlings, which did not receive supplementary food during the postnatal period, had higher oxidative damage than male nestlings. On the other hand, no differences in the oxidative status of males and females were found when they, pre- or postnatally, received supplementary food. This results show that nutritional conditions experienced early in life, and also already before birth, influence the oxidative status of offspring in a sex-specific way, suggesting sex-specific resource-allocation strategies early in life. In Chapter three, I set out to test how food availability during egg laying affects a female’s condition and reproductive effort, and to test whether the eggshell pigmentation pattern signals the oxidative status of the female, as predicted by the ‘sexual signaling hypothesis’. I found that the food availability experienced by females during reproduction affects their level of oxidative damage, with females experiencing higher food availability suffering of lower levels of oxidative stress. Moreover, the nutritional and oxidative condition of the females interactively modulated the allocation of antioxidants in the eggs, and female and yolk antioxidant capacity related to the pattern of eggshell pigmentation. These findings support the prediction of the ‘sexual signaling hypothesis’ and they shed further light on the mechanisms underlying the costs of reproduction.

The environment experienced by an organism at different life stages can have substantial effects on its phenotype. The environmental conditions the mother encounters can substantially influence her investment in the present reproductive attempt, and the phenotype of her offspring through the so-called maternal effects. Moreover, prenatal and early postnatal conditions experienced by offspring can interact and modulate their life histories. The aim of this thesis is to give new insight into environmentally induced maternal effects and to test the effects of the interaction between pre- and early postnatal conditions on offspring physiology and morphology in a wild-living bird species, the great tit (Parus major). In Chapter one, I investigated how an environmental match / mismatch between the food availability encountered by mothers during egg laying (i.e. prenatal environment) and by nestlings during early growth affected the developmental trajectories of nestlings, testing for a possible role of yolk androgens in mediating potential prenatal maternal effects. I found no evidence that nestlings performed better when experiencing matching nutritional conditions. However, being raised in the original nest by the biological parents (i.e. matching conditions) had positive effects on nestling growth and body mass. I was able to show significant interactive effects of pre- and postnatal food availability on nestling body growth, and significant effects of maternal food availability on nestling body size and mass. However, these effects were not mediated by yolk androgen deposition. The results of this experiment suggest that food-induced maternal effects can have substantial effects on fitness-related traits of the offspring by influencing their efficiency to use nutritional resources. They also highlight the necessity to take multiple environmental factors into account when studying the effects of environmental match / mismatch on offspring phenotype. In Chapter two I assessed how pre- and early postnatal nutritional conditions and their match / mismatch can affect the physiological conditions, measured as oxidative status, of male and female nestling great tits. My findings revealed that the nutritional conditions experienced by mothers and by offspring during growth affect the physiological condition of nestlings in a sex-specific way. Female nestlings whose mother has not been food-supplemented, and female nestlings, which did not receive supplementary food during the postnatal period, had higher oxidative damage than male nestlings. On the other hand, no differences in the oxidative status of males and females were found when they, pre- or postnatally, received supplementary food. This results show that nutritional conditions experienced early in life, and also already before birth, influence the oxidative status of offspring in a sex-specific way, suggesting sex-specific resource-allocation strategies early in life. In Chapter three, I set out to test how food availability during egg laying affects a female’s condition and reproductive effort, and to test whether the eggshell pigmentation pattern signals the oxidative status of the female, as predicted by the ‘sexual signaling hypothesis’. I found that the food availability experienced by females during reproduction affects their level of oxidative damage, with females experiencing higher food availability suffering of lower levels of oxidative stress. Moreover, the nutritional and oxidative condition of the females interactively modulated the allocation of antioxidants in the eggs, and female and yolk antioxidant capacity related to the pattern of eggshell pigmentation. These findings support the prediction of the ‘sexual signaling hypothesis’ and they shed further light on the mechanisms underlying the costs of reproduction.

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Additional indexing

Item Type:Dissertation
Referees:Tschirren Barbara, Hau Michaela, Räsänen Katja, Jenny-Eiermann Susi, Keller Lukas F, Spencer Karen
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:7 November 2014
Deposited On:16 Dec 2014 15:48
Last Modified:05 Apr 2016 18:39
Funders:Swiss National Science Foundation
Permanent URL: https://doi.org/10.5167/uzh-102666

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