Genetic, environmental and maternal effects on magpie nestling-fitness traits under different nutritional conditions: a new experimental approach
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URI: https://hdl.handle.net/10481/87257Metadata
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2004Abstract
Rearing full siblings under different environmental conditions allows partitioning of the total
phenotypic variance of a trait into its genetic and environmental components. This, in natural
bird populations, is usually achieved by cross-fostering experimental designs. We estimated
genetic and environmental components of nestling-fitness traits using an alternative
experimental approach in a magpie (Pica pica) population. Two broods of full siblings were
reared under contrasting environmental conditions of first and replacement clutches. With this
approach, potential maternal effects related to differences in clutch size and egg size could also
be partially evaluated. In addition, the nutritional condition of half of the nestlings within each
nest was manipulated by providing a calorie-rich paste enriched with micronutrients. Our
results are only indicative because of very low sample sizes. In food-supplemented nestlings, the
heritability estimates of tarsus length, body mass and T-cell-mediated immune response tended
to be higher compared with control nestlings. No causal conclusions could be drawn for
changes in heritability estimates of body mass and T-cell-mediated immune response; for
tarsus length, the results suggest a lower potential to adapt to poor nutritional conditions.
Furthermore, we found some indication that maternal effects related to clutch/egg size inflated
causal estimates of phenotypic variance in tarsus length.