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）通常被认为会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为人知。既往研究多聚焦于信号与生存间的线性关联，但根据性状表达的主要成本差异，也可预测出驼峰形与U形的关联模式。此外，鲜有研究在生存选择分析中考虑信号的可塑性。基于黑色素的性状（melanin-based trait）中，信号表达与生存的关联尤为受关注，因为这类性状的主要成本仍存在争议。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主要影响因素：一种群居鸟类——群居织巢鸟（Philetairus socius）的喉斑大小。随后基于上述分析结果，我们获得了可代表个体喉斑平均表达水平的量化指标。最后，我们采用捕获再捕获模型（capture-recapture models）分析了喉斑大小与生存概率的变化关系。喉斑大小的变异受年份影响显著，同时也受年龄、身体状态以及种群规模的中等程度影响。此外，喉斑偏小或偏大的个体生存概率高于喉斑处于中等水平的个体，且这种生存与喉斑大小间的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提供了罕见的实例，同时表明地位徽章的优势信号功能所带来的社会成本可能具有重要意义。