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Geographical trends in the yolk carotenoid composition of the pied flycatcher (Ficedula hypoleuca).

Eeva T, Ruuskanen S, Salminen JP, Belskii E, Järvinen A, Kerimov A, Korpimäki E, Krams I, Moreno J, Morosinotto C, Mänd R, Orell M, Qvarnström A, Siitari H, Slater FM, Tilgar V, Visser ME, Winkel W, Zang H, Laaksonen T - Oecologia (2010)

Bottom Line: We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards.Concentrations of β-carotene and zeaxanthin did not show any obvious geographical gradients.Further studies are needed to test the fitness effects of this geographical variation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Turku, Turku, Finland. tapio.eeva@utu.fi

ABSTRACT
Carotenoids in the egg yolks of birds are considered to be important antioxidants and immune stimulants during the rapid growth of embryos. Yolk carotenoid composition is strongly affected by the carotenoid composition of the female's diet at the time of egg formation. Spatial and temporal differences in carotenoid availability may thus be reflected in yolk concentrations. To assess whether yolk carotenoid concentrations or carotenoid profiles show any large-scale geographical trends or differences among habitats, we collected yolk samples from 16 European populations of the pied flycatcher, Ficedula hypoleuca. We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards. The most southern population (which is also the one found at the highest altitude) also showed relatively low carotenoid levels. Concentrations of β-carotene and zeaxanthin did not show any obvious geographical gradients. Egg yolks also contained proportionally more lutein and other xanthophylls in deciduous than in mixed or coniferous habitats. We suggest that latitudinal gradients in lutein and xanthophylls reflect the lower availability of lutein-rich food items in the northern F. hypoleuca populations and in montane southern populations, which start egg-laying earlier relative to tree phenology than the Central European populations. Similarly, among-habitat variation is likely to reflect the better availability of lutein-rich food in deciduous forests. Our study is the first to indicate that the concentration and profile of yolk carotenoids may show large-scale spatial variation among populations in different parts of the species' geographical range. Further studies are needed to test the fitness effects of this geographical variation.

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Mean carotenoid concentrations (d.w.) in egg yolks of Ficedula hypoleuca in 16 European populations. Populations are sorted in ascending order according to latitude (see Fig. 1). Letters refer to the populations listed in Table 1
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Fig2: Mean carotenoid concentrations (d.w.) in egg yolks of Ficedula hypoleuca in 16 European populations. Populations are sorted in ascending order according to latitude (see Fig. 1). Letters refer to the populations listed in Table 1

Mentions: We tested the relationships between yolk carotenoid concentrations (lutein, zeaxanthin, other xanthophylls, β-carotene, unidentified carotenoids and total; Fig. 2) and geographic location with generalized linear mixed models (GLMM) in the Glimmix procedure of SAS (SAS Institute 2003). The independent factors in the models were: latitude, longitude, altitude (m.a.s.l.), second-order terms of latitude and longitude, habitat (coniferous, mixed, deciduous), habitat × latitude and habitat × longitude. Altitude was included in the models as a confounding factor, since there was considerable variation in altitude among sampling sites (Table 1) and altitude may affect the diet of birds (e.g., via differences in vegetation and phenology). None of the carotenoid concentrations were correlated with clutch size (n = 155, r = −0.081 to 0.13, p > 0.05 in all) or yolk mass (n = 142, r = −0.11 to 0.054, p > 0.05 in all), and these possible confounding variables were not included in the models. In these models, we used lognormal (to the base e) error distribution and population as random factors. Since some of our sampling sites were closer to one another than others, we first checked whether there was spatial autocorrelation in model residuals. Moran’s I coefficients ranged from −0.039 to −0.041 (n = 162), indicating a slight negative autocorrelation in the data. However, adding Gaussian or exponential spatial covariance structure to the models did not increase the model fit, as compared with the AIC values. Therefore, a default covariance structure (variance components) was used. Non-significant terms were dropped from the models one-by-one, starting from the interactions. The dropped main effects were again added to the reduced models one at a time, but in no case were they significant, and they were not included in the final models. Since our sample included both third and fourth eggs in laying order, we further checked if this variation in laying order explained any of the yolk carotenoid concentrations. We ran all the final models (lutein, zeaxanthin, other xanthophylls, β-carotene, unidentified carotenoids and total) with egg number added as a further explanatory factor. However, in no case was the effect of laying order significant. Degrees of freedom were calculated with the Kenward–Roger method. Pairwise post hoc comparisons between habitats were made with Tukey’s test.Fig. 2


Geographical trends in the yolk carotenoid composition of the pied flycatcher (Ficedula hypoleuca).

Eeva T, Ruuskanen S, Salminen JP, Belskii E, Järvinen A, Kerimov A, Korpimäki E, Krams I, Moreno J, Morosinotto C, Mänd R, Orell M, Qvarnström A, Siitari H, Slater FM, Tilgar V, Visser ME, Winkel W, Zang H, Laaksonen T - Oecologia (2010)

Mean carotenoid concentrations (d.w.) in egg yolks of Ficedula hypoleuca in 16 European populations. Populations are sorted in ascending order according to latitude (see Fig. 1). Letters refer to the populations listed in Table 1
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3197936&req=5

Fig2: Mean carotenoid concentrations (d.w.) in egg yolks of Ficedula hypoleuca in 16 European populations. Populations are sorted in ascending order according to latitude (see Fig. 1). Letters refer to the populations listed in Table 1
Mentions: We tested the relationships between yolk carotenoid concentrations (lutein, zeaxanthin, other xanthophylls, β-carotene, unidentified carotenoids and total; Fig. 2) and geographic location with generalized linear mixed models (GLMM) in the Glimmix procedure of SAS (SAS Institute 2003). The independent factors in the models were: latitude, longitude, altitude (m.a.s.l.), second-order terms of latitude and longitude, habitat (coniferous, mixed, deciduous), habitat × latitude and habitat × longitude. Altitude was included in the models as a confounding factor, since there was considerable variation in altitude among sampling sites (Table 1) and altitude may affect the diet of birds (e.g., via differences in vegetation and phenology). None of the carotenoid concentrations were correlated with clutch size (n = 155, r = −0.081 to 0.13, p > 0.05 in all) or yolk mass (n = 142, r = −0.11 to 0.054, p > 0.05 in all), and these possible confounding variables were not included in the models. In these models, we used lognormal (to the base e) error distribution and population as random factors. Since some of our sampling sites were closer to one another than others, we first checked whether there was spatial autocorrelation in model residuals. Moran’s I coefficients ranged from −0.039 to −0.041 (n = 162), indicating a slight negative autocorrelation in the data. However, adding Gaussian or exponential spatial covariance structure to the models did not increase the model fit, as compared with the AIC values. Therefore, a default covariance structure (variance components) was used. Non-significant terms were dropped from the models one-by-one, starting from the interactions. The dropped main effects were again added to the reduced models one at a time, but in no case were they significant, and they were not included in the final models. Since our sample included both third and fourth eggs in laying order, we further checked if this variation in laying order explained any of the yolk carotenoid concentrations. We ran all the final models (lutein, zeaxanthin, other xanthophylls, β-carotene, unidentified carotenoids and total) with egg number added as a further explanatory factor. However, in no case was the effect of laying order significant. Degrees of freedom were calculated with the Kenward–Roger method. Pairwise post hoc comparisons between habitats were made with Tukey’s test.Fig. 2

Bottom Line: We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards.Concentrations of β-carotene and zeaxanthin did not show any obvious geographical gradients.Further studies are needed to test the fitness effects of this geographical variation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Turku, Turku, Finland. tapio.eeva@utu.fi

ABSTRACT
Carotenoids in the egg yolks of birds are considered to be important antioxidants and immune stimulants during the rapid growth of embryos. Yolk carotenoid composition is strongly affected by the carotenoid composition of the female's diet at the time of egg formation. Spatial and temporal differences in carotenoid availability may thus be reflected in yolk concentrations. To assess whether yolk carotenoid concentrations or carotenoid profiles show any large-scale geographical trends or differences among habitats, we collected yolk samples from 16 European populations of the pied flycatcher, Ficedula hypoleuca. We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards. The most southern population (which is also the one found at the highest altitude) also showed relatively low carotenoid levels. Concentrations of β-carotene and zeaxanthin did not show any obvious geographical gradients. Egg yolks also contained proportionally more lutein and other xanthophylls in deciduous than in mixed or coniferous habitats. We suggest that latitudinal gradients in lutein and xanthophylls reflect the lower availability of lutein-rich food items in the northern F. hypoleuca populations and in montane southern populations, which start egg-laying earlier relative to tree phenology than the Central European populations. Similarly, among-habitat variation is likely to reflect the better availability of lutein-rich food in deciduous forests. Our study is the first to indicate that the concentration and profile of yolk carotenoids may show large-scale spatial variation among populations in different parts of the species' geographical range. Further studies are needed to test the fitness effects of this geographical variation.

Show MeSH