Data from: Covariation in life-history traits: differential effects of diet on condition, hormones, behavior and reproduction in genetic finch morphs

The relative contribution of genetic and environmental factors in determining variation in life-history traits is of central interest to evolutionary biologists, but the physiological mechanisms underlying these traits are still poorly understood. Here we experimentally demonstrate opposing effects of nutritional stress on immune function, endocrine physiology, parental care and reproduction between red and black head-color morphs of the Gouldian finch (Erythrura gouldiae). Although body condition of black morphs was largely unaffected by diet manipulation, red birds were highly sensitive to dietary changes, exhibiting considerable within-individual changes in condition and immune function. Consequently, nutritionally stressed red birds delayed breeding, produced smaller broods and reared fewer and lower-quality foster offspring than black morphs. Differences in offspring quality were largely due to morph-specific differences in parental effort; red morphs reduced parental provisioning, whereas black morphs adaptively elevated their provisioning effort to meet the increased nutritional demands of their foster brood. Nutritionally stressed genetic morphs also exhibited divergent glucocorticoid responses. Black morphs showed reduced corticosterone-binding globulin (CBG) concentrations and increased levels of free corticosterone, whereas red morphs exhibited reduced free corticosterone levels and elevated CBG concentrations. These opposing glucocorticoid responses highlight intrinsic differences in endocrine sensitivities and plasticity between genetic morphs, which may underlie the morph-specific differences in condition, behavior and reproduction, and thus ultimately contribute to the evolution and maintenance of color polymorphism.遗传与环境因素对生活史性状变异的相对贡献，是进化生物学家的核心研究议题，但这些性状背后的生理机制仍有待深入阐明。本研究通过实验证实，营养胁迫对七彩文鸟（Erythrura gouldiae）红头与黑头两种头部色型的免疫功能、内分泌生理、育幼行为以及繁殖产生了相反的影响。尽管黑头色型的身体状况基本不受日粮调控的影响，红头个体却对日粮变化极为敏感，其身体状况与免疫功能均出现了显著的个体内变化。因此，经历营养胁迫的红头个体相比黑头色型，繁殖周期延迟、窝卵数更少，且抚育的寄养后代数量更少、质量更低。子代质量的差异主要源于两种色型亲代投入的特异性差异：红头色型降低了育雏投喂行为，而黑头色型则适应性地提升了投喂投入，以满足寄养雏鸟增加的营养需求。经历营养胁迫的两种遗传色型，其糖皮质激素响应也存在显著分化。黑头色型的皮质酮结合球蛋白（corticosterone-binding globulin, CBG）浓度降低，游离皮质酮水平升高；而红头色型则表现为游离皮质酮水平降低，CBG浓度升高。这种相反的糖皮质激素响应，揭示了两种遗传色型在内分泌敏感性与可塑性上的内在差异，而这或许正是不同色型在身体状况、行为与繁殖上出现特异性差异的基础，并最终推动了颜色多态性的演化与维持。