There is growing evidence of important variation in how animals age, in particular in how the expression of traits changes with age among different species and populations. However, less is known about variation within populations, which may include variation in ageing patterns between different types of individuals (e.g. sexes or distinct polymorphisms) and between different types of traits (e.g. general traits versus those used in social signalling contexts). We used 6 years of longitudinal data to examine age-related changes in trait expression in a captive population of Gouldian finches (Erythrura gouldiae), a socially monogamous songbird with genetically determined colour morphs that differ in behaviour and physiology. We contrasted ageing patterns of different types of traits (social signalling vs. size-related) in both sexes and in two colour morphs, using a mixed model approach to account for both within- and between-individual effects. We found pronounced sex differences in how social signalling traits change with age, showing a quadratic pattern in males, but not changing with age in females. In contrast, we observed no sex-specific ageing patterns in size traits. We also found subtle morph differences in how size-related traits changed with age, with black morphs stable or increasing with age while red morphs showing a decline with age. Finally, we found an interesting sex by morph interaction in one important social signal (headband width). These results highlight the importance of using within-individual approaches to understand ageing patterns across types of individuals (sex, morph, etc.) and the need for further research on the ageing patterns of traits that may experience different selective pressures.

中文翻译：

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多态鸣禽的年龄依赖性性状变化中的性别和形态差异。

越来越多的证据表明动物衰老的方式存在重要差异，特别是在不同物种和种群之间性状的表达如何随年龄变化方面。然而，人们对群体内的变异知之甚少，这可能包括不同类型个体（例如性别或不同的多态性）之间以及不同类型特征之间（例如一般特征与社会信号环境中使用的特征）之间的衰老模式差异。我们使用 6 年的纵向数据来检查 Gouldian 雀 (Erythrura gouldiae) 圈养种群中与年龄相关的性状表达变化，这是一种社会一夫一妻制的鸣禽，具有在行为和生理学上不同的遗传决定的颜色形态。我们对比了不同类型特征的衰老模式（社交信号与社交信号）。尺寸相关）在两种性别和两种颜色变形中，使用混合模型方法来解释个体内部和个体之间的影响。我们发现社会信号特征如何随年龄变化存在明显的性别差异，在男性中显示出二次模式，但在女性中不随年龄变化。相比之下，我们在体型特征中没有观察到性别特异性的衰老模式。我们还发现与大小相关的特征如何随年龄变化的细微变形差异，黑色变形随着年龄的增长稳定或增加，而红色变形随着年龄的增长而下降。最后，我们在一个重要的社交信号（头带宽度）中通过变形交互发现了一种有趣的性别。这些结果强调了使用个体内部方法来了解不同类型个体（性别、变形等）的衰老模式的重要性。