Data from: Contrasting patterns of selection on the size and coloration of a female plumage ornament in common yellowthroats

Females often possess ornaments that appear smaller and duller than homologous traits in males. These ornaments may arise as nonfunctional by-products of sexual selection in males and cause negative viability or fecundity selection in females in proportion to the cost of their production and maintenance. Alternatively, female ornaments may function as signals of quality that are maintained by sexual or social selection. In a 4-year study of 83 female common yellowthroats (Geothlypis trichas) and their 222 young, we found strong viability and fecundity selection on the yellow bib, a carotenoid-based plumage ornament that is a target of sexual selection in males. Females with larger bibs were older, larger and more fecund than females with smaller bibs. However, bib size positively covaried with bib total brightness and carotenoid chroma, aspects of bib coloration that were under negative viability and fecundity selection. Females with more colourful bibs laid fewer eggs in their first clutch, were more likely to suffer total brood loss due to predation and were less likely to return to the study area. Selection against bib coloration limits the value of bib size as a quality indicator in females and may constrain the elaboration of bib attributes in males.

雌性个体通常拥有相较于雄性同源性状更小、更黯淡的装饰结构。这类装饰可能作为雄性性选择产生的非功能性副产物出现，其对雌性施加的负向存活力选择或繁殖力选择强度，与其产生和维持的成本成正比。另一方面，雌性装饰也可作为个体质量的信号，通过性选择或社会选择得以保留。在一项针对83只雌性黄喉地莺（Geothlypis trichas）及其222只雏鸟的为期4年的研究中，我们发现针对黄色围斑——一种基于类胡萝卜素的羽饰（carotenoid-based plumage ornament），同时也是雄性性选择的靶标性状——存在强烈的存活力与繁殖力选择。喉斑更大的雌性个体年龄更大、体型更大，且繁殖力高于喉斑更小的雌性。然而，喉斑大小与喉斑总亮度及类胡萝卜素色度呈正相关，而喉斑着色的这两个维度正承受负向的存活力与繁殖力选择。喉斑色彩更艳丽的雌性，其首窝产卵量更少，更易因捕食发生全巢损失，且返回研究区域的概率更低。针对喉斑着色的选择限制了喉斑大小作为雌性个体质量指示信号的价值，同时或会制约雄性喉斑相关性状的演化强化。