Data from: Evolutionary potential of morphological traits across different life-history stages

Despite accumulating examples of selection acting on heritable traits in the wild, predicted evolutionary responses are often different from observed phenotypic trends. Various explanations have been suggested for these mismatches. These include within-individual changes across lifespan that can create important variation in genetic architecture of traits and selection acting on them, but also potential problems with the methodological approach used to predict evolutionary responses of traits. Here, we used an 8-year data set on tree swallow (Tachycineta bicolor) to first assess the effects of differences among three nestling life-history stages on the genetic (co)variances of two morphological traits (body mass and primary feather length) and the selection acting on them over three generations. We then estimated the evolutionary potential of these traits by predicting their evolutionary responses using the breeder's equation and the secondary theorem of selection approaches. Our results showed variation in strength and direction of selection and slight changes in trait variance across ages. Predicted evolutionary responses differed importantly between both approaches for half of the trait–age combinations we studied, suggesting the presence of environmentally induced correlations between focal traits and fitness possibly biasing breeder's equation predictions. Our results emphasize that predictions of evolutionary potential for morphological traits are likely to be highly variable, both in strength and direction, depending on the life stage and method used, thus mitigating our capacity to predict adaptation and persistence of wild populations.

尽管学界已积累诸多野生种群中选择作用于可遗传性状的实证案例，但预测得到的进化响应往往与观测到的表型趋势并不一致。针对这类偏差，学界已提出多种解释路径。这些解释既涵盖个体在整个生命周期内的生理变化——这类变化可对性状的遗传结构及作用于其上的选择压力造成显著影响——也包含用于预测性状进化响应的方法论手段可能存在的潜在缺陷。本研究以一套为期8年的双色树燕（Tachycineta bicolor）观测数据集为基础，首先探究了三个雏鸟生活史阶段间的差异对两种形态性状（体重与初级飞羽长度）的遗传（共）方差以及三代间作用于这些性状的选择压力的影响。随后，我们分别借助育种者方程（breeder's equation）与选择次级定理（secondary theorem of selection）两种分析方法，通过预测进化响应来估算这些性状的进化潜力。研究结果显示，选择压力的强度与方向存在变异，且不同日龄的性状方差存在小幅变化。针对我们研究的半数性状-日龄组合，两种方法得到的预测进化响应存在显著差异，这表明目标性状与适合度之间可能存在环境诱导的相关性，进而可能使育种者方程的预测结果产生偏倚。本研究结果强调，形态性状的进化潜力预测结果很可能在强度与方向上存在高度变异，这取决于所选取的生活史阶段与研究方法，进而限制了我们精准预测野生种群适应与存续情况的能力。