Data from: No mutual mate choice for quality in zebra finches: time to question a widely-held assumption

Studies of mate choice typically assume that individuals prefer high quality mates and select them based on condition-dependent indicator traits. In species with bi-parental care, mutual mate choice is expected to result in assortative mating for quality. When assortment is not perfect, the lower quality pair members are expected to compensate by increased parental investment to secure their partner (positive differential allocation). This framework has been assumed to hold for monogamous species like the zebra finch (Taeniopygia guttata), but progress has been hampered by the difficulty to define individual quality. By combining multiple measures of causes (inbreeding, early nutrition) and consequences (ornaments, displays, fitness components) of variation in quality into a single principal component, we here show that quality variation can be quantified successfully. We further show that variation in quality indeed predicts individual pairing success, presumably because it reflects an individual's vigor or ability to invest in reproduction. However, despite high statistical power, we found no evidence for either assortative mating or for positive differential allocation. We suggest that zebra finch ornaments and displays are not sufficiently reliable for the benefits of choosiness to exceed the costs of competition for the putative best partner. To assess the generality of these findings unbiased quantification of signal honesty and preference strength is required, rather than selective reporting of significant results.择偶研究通常默认，个体会偏好高品质配偶，并依据条件依赖型指示性状完成配偶选择。在存在双亲照料（bi-parental care）的物种中，双向配偶选择理论上会导致基于个体品质的选型交配（assortative mating）。当配对的品质匹配度并非完美时，低品质的配偶个体预计会通过提升亲本投入（parental investment）来补偿自身不足，以稳固伴侣关系，该机制即正向差异分配（positive differential allocation）。该理论框架曾被认为适用于斑胸草雀（zebra finch, Taeniopygia guttata）这类单配制物种（monogamous species），但由于难以精准界定个体品质，相关研究进展长期受阻。我们将个体品质变异的多项成因（近交（inbreeding）、早期营养状况）与表现后果（饰羽（ornaments）、展示行为（displays）、适合度组分（fitness components））整合为单一主成分（principal component），最终成功实现了对品质变异的量化。我们进一步证实，个体品质变异确实能够预测其配对成功率，这大概率是因为品质反映了个体的活力或繁殖投入能力。然而，尽管本研究具备充足的统计效力，我们并未发现任何支持选型交配或正向差异分配的证据。我们推测，斑胸草雀的饰羽与展示行为的可靠程度不足，以至于择偶偏好所能带来的收益，未能超过争夺所谓最优配偶所需付出的竞争成本。若要评估这些发现的普适性，需对信号诚实性与偏好强度开展无偏量化研究，而非选择性报道具有统计学显著性的实验结果。