Variation in oxidative status, but not structural and physiological development, associated with changing ontogenetic...

Area of Science:

• * Evolutionary Biology
• * Developmental Biology
• * Ornithology

Background:

• * Canalization, the robustness of trait development to environmental variation, is crucial for fitness.
• * Understanding how developmental stage influences canalization is vital, especially during life-stage transitions like fledging.
• * Previous research has rarely considered the impact of developmental stage on trait canalization.

Purpose of the Study:

• * To investigate the sensitivity of morphological and physiological traits to environmental variation across two developmental stages in European starlings (Sturnus vulgaris).
• * To determine if trait canalization observed in early development persists into late development, particularly during the pre-fledging period.

Main Methods:

• * Experimental manipulation of brood size at hatching in European starlings.
• * Cross-fostering of chicks between high and low-quality environments during late development (approaching fledging).
• * Measurement of body size (mass, tarsus, wing length), aerobic capacity, and oxidative status at two time points (day 15 and day 20).

Main Results:

• * Chicks in reduced broods were heavier and had lower reactive oxygen metabolites at asymptotic mass (day 15).
• * Structural size, aerobic capacity, and antioxidant capacity were largely unaffected by experimental brood size in early development.
• * Canalization of structural and physiological traits persisted into late development, but antioxidant capacity showed sensitivity to cross-fostering treatments.
• * Elevated reactive oxygen metabolites in enlarged brood chicks during early development were maintained after cross-fostering, indicating carry-over oxidative costs.

Conclusions:

• * Trait-specific canalization varies with developmental stage, with antioxidant capacity becoming more environmentally sensitive as fledging approaches.
• * Canalized development in low-quality environments can incur oxidative costs that persist even when conditions improve.
• * Natal environment effects on development are stage-dependent, highlighting the complexity of trait robustness throughout an organism's life cycle.