Biology Department, Advanced Facility for Avian Research, University of Western Ontario, London, Canada N6A 5B7.
Psychology Department, Advanced Facility for Avian Research, University of Western Ontario, London, Canada N6A 5C2.
Biol Lett. 2018 Jul;14(7). doi: 10.1098/rsbl.2018.0194.
Immune defences often trade off with other life-history components. Within species, optimal allocation to immunity may differ between the sexes or between alternative life-history strategies. White-throated sparrows () are unusual in having two discrete plumage morphs, white-striped and tan-striped. Within each sex, white-striped individuals are more aggressive and provide less parental care than tan-striped individuals. We extended immunocompetence handicap models, which predict sex differences in immunity and parasitism, to hypothesize that infection susceptibility should be greater in white-striped than tan-striped birds. We inoculated birds of both morphs with malarial parasites. Contrary to our prediction, among birds that became infected, parasite loads were higher in tan-striped than white-striped individuals and did not differ between the sexes. Circulating androgen levels did not differ between morphs but were higher in males than females. Our findings are not consistent with androgen-mediated immunosuppression. Instead, morph differences in immunity could reflect social interactions or life-history-related differences in risk of injury, and/or genetic factors. Although plumage and behavioural morphs of white-throated sparrow may differ in disease resistance, these differences do not parallel sex differences that have been reported in animals, and do not appear to be mediated by differences in androgen levels.
免疫防御通常与其他生活史特征相互权衡。在同一物种中，免疫的最佳分配可能因性别或替代生活史策略而异。白喉雀（）的一个独特之处在于其具有两种截然不同的羽色形态，即白条和棕条。在每个性别中，白条个体比棕条个体更具攻击性，提供的亲代抚育也较少。我们扩展了免疫能力障碍模型，该模型预测了性别间免疫和寄生虫感染的差异，假设白条个体比棕条个体更容易感染。我们用疟原虫感染了这两种形态的鸟类。与我们的预测相反，在感染的鸟类中，棕条个体的寄生虫负荷高于白条个体，而且这种差异在性别间不存在。循环雄激素水平在形态间没有差异，但在雄性中高于雌性。我们的研究结果与雄激素介导的免疫抑制不一致。相反，免疫方面的形态差异可能反映了社会互动或与生活史相关的受伤风险差异，以及/或遗传因素。尽管白喉雀的羽色和行为形态在疾病抵抗力方面可能存在差异，但这些差异与动物中报道的性别差异并不一致，而且似乎不受雄激素水平差异的影响。
