Data from: Disruptive viability selection on a black plumage trait associated with dominance

Traits used in communication, such as colour signals, are expected to have positive consequences for reproductive success, but their associations with survival are little understood. Previous studies have mainly investigated linear relationships between signals and survival, but both hump-shaped and U-shaped relationships can also be predicted, depending on the main costs involved in trait expression. Furthermore, few studies have taken the plasticity of signals into account in viability selection analyses. The relationship between signal expression and survival is of particular interest in melanin-based traits, because their main costs are still debated. Here, we first determined the main factors explaining variability in a melanin-based trait linked to dominance: the bib size of a colonial bird, the sociable weaver Philetairus socius. We then used these analyses to obtain a measure representative of the individual mean expression of bib size. Finally, we used capture-recapture models to study how survival varied in relation to bib size. Variation in bib size was strongly affected by year and moderately affected by age, body condition and colony size. In addition, individuals bearing small and large bibs had higher survival than those with intermediate bibs, and this U-shaped relationship between survival and bib size appeared to be more pronounced in some years than others. These results constitute a rare example of disruptive viability selection, and point towards the potential importance of social costs incurred by the dominance signalling function of badges of status.用于通讯交流的性状（如色彩信号）通常被认为可对繁殖成功率产生积极影响，但这类性状与生存之间的关联却鲜有研究探明。既往相关研究多聚焦于信号与生存间的线性关联，但根据性状表达所涉及的核心成本差异，也可推导出驼峰形与U形的关联模式。此外，鲜有研究在生存选择分析中纳入信号可塑性这一因素。 基于黑色素的性状（melanin-based traits）中，信号表达与生存的关联尤为受学界关注，因为这类性状的核心成本仍存在学术争议。本研究首先明确了与优势地位相关的基于黑色素的性状变异的核心影响因素：群居鸟类——群居织巢鸟（*Philetairus socius*）的胸斑大小。随后，基于上述分析结果，我们得到了可代表个体胸斑平均表达水平的量化指标。最后，我们借助标记重捕模型（capture-recapture models）分析了生存概率随胸斑大小的变化规律。 胸斑大小的变异受年份影响极强，同时也受到年龄、身体状况以及种群规模的中等程度影响。此外，胸斑尺寸偏小与偏大的个体存活率均高于胸斑尺寸处于中间水平的个体，且这种生存与胸斑大小间的U形关联在部分年份中表现得更为显著。 本研究结果为破坏性生存选择（disruptive viability selection）提供了一则罕见实例，同时表明地位徽章（badges of status）的优势信号功能所引发的社会成本可能具有重要研究价值。