Environmental effects shape the maternal transfer of carotenoids and vitamin E to the yolk

There was a significant effect of the current environmental conditions on the yolk carotenoid and vitamin E deposition, but this effect varied between antioxidant components. The deposition of yolk carotenoids and vitamin E were linked to the process of yolk formation. Past environmental conditions did not contribute to the variation in yolk carotenoid and vitamin E levels nor did we find significant heritable variation.The transfer of carotenoids or vitamin E may be an example where current environmental variation is largely passed from the mother to the offspring, despite the numerous intermediate physiological steps that are involved. Differences in the effect of the environmental conditions as experienced by the mother during laying may be due to differences in availability as well as physiological processes such as competitive exclusion or selective absorption.Maternal effects occur when offspring phenotype is influenced by the phenotype of the mother, which in turn depends on the environmental conditions the mother experiences as well as on her - partly heritable - physiological state [1,2]. Maternal effects are thought to have evolved to match the phenotype of the offspring to (changes in) their environment (‘adaptive maternal effects’) [1-3]. A main focus of research has, therefore, been on identifying environmental sources of variation in maternal effects. This has been particularly well studied in birds, where egg size and composition can be considered as important maternal traits that generate significant changes in offspring phenotype [4-6]. More specifically, several recent studies have focused on a number of specific egg components such as hormones, antibodies, carotenoids and vitamins [e.g. [4,5,7,8]. In case of the latter two, there is now a large body of evidence for environmental effects modifying the maternal deposition of carotenoids and vitamins [e.g. [7-12].However, maternal effects not only have an environmental but also a genetic component [2