Data from: Plumage color manipulation has no effect on social dominance or fitness in zebra finches

Colourful plumage ornaments may evolve because they play a role in mate choice or in intrasexual competition, acting as signals of species identity or of individual quality. The zebra finch (Taeniopygia guttata) is a model organism for the study of mate choice and its colourful plumage ornaments are thought to be used in both of these contexts. Numerous genetic colour variants have been described for this species, but they are rare in the wild. This raises the question whether discrimination against deviant phenotypes maintains the species’ uniform plumage colour (rare mate disadvantage). Further, comparison to closely related species suggests that the lack of colourful ornaments in female zebra finches is a derived condition. Male preferences for less ornamented females may have led to sexual dichromatism in the zebra finch. Here, we test the role of plumage ornaments experimentally by altering male and female colouration to mimic two types of naturally occurring genetic colour variants. We estimated effects on social dominance and reproductive success in large breeding aviaries in one domesticated and two recently wild-derived populations. Hypotheses, methods and analyses were preregistered to ensure maximal objectivity of the results presented. Despite a fairly drastic manipulation and a powerful experimental design, we found no effect of the treatment on social dominance or on reproductive success. Our results suggest that mate choice is not the mechanism that maintains homogeneity of zebra finch plumage colouration, or that can explain the loss of ornaments in females.

色彩艳丽的羽饰之所以能够演化，或许是因为其在配偶选择或种内竞争中发挥作用，作为物种身份或个体品质的信号。斑胸草雀（Taeniopygia guttata）是配偶选择研究的模式生物，其色彩艳丽的羽饰被认为在这两类场景中均有应用。该物种已被描述出多种遗传色型，但在野生环境中极为罕见。这引出了一个问题：对异常表型的判别是否维持了该物种统一的羽色（即稀有配偶劣势）。进一步而言，与近缘物种的对比显示，雌性斑胸草雀缺乏彩色羽饰是一种衍征状态。雄性对装饰程度较低的雌性的偏好，或许造就了斑胸草雀的性二色性。本研究通过人工改变雄性和雌性的羽色，以模拟两种自然存在的遗传色型，实验性地检验羽饰的作用。我们在一个驯化种群和两个新近野生来源的种群的大型繁殖鸟舍中，评估了该处理对社会支配地位与繁殖成功率的影响。本研究的假设、方法与分析均已预先注册，以确保所呈现结果的最大客观性。尽管采用了相当彻底的操纵手段与严谨有力的实验设计，我们并未发现该处理对社会支配地位或繁殖成功率存在影响。我们的结果表明，配偶选择并非维持斑胸草雀羽色均一性的机制，亦无法解释雌性斑胸草雀羽饰的缺失。