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 dataset 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.

尽管已有大量研究证实选择在野生种群中作用于可遗传性状，但预测得到的进化响应往往与观测到的表型趋势存在偏差。针对此类预测与观测结果间的不匹配现象，学界已提出多种解释。此类解释涵盖：个体在整个生命周期内发生的表型变化可对性状的遗传结构及其所受选择造成显著变异；此外，用于预测性状进化响应的研究方法本身亦可能存在潜在缺陷。本研究依托一项针对树燕（Tree swallow，Tachycineta bicolor）的8年监测数据集，首先评估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）方差及其在三代间所受选择的影响。随后，本研究借助育种者方程（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，选择的强度与方向存在变异，且各雏鸟生活史阶段的性状方差存在小幅变化。针对本次研究涉及的半数性状-生活史阶段组合，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（fitness）之间可能存在环境诱导的相关性，进而对育种者方程的预测结果造成偏倚。本研究结果表明，形态性状的进化潜力预测结果可能在强度与方向上均存在显著变异，且这一变异取决于所选取的生活史阶段与分析方法，进而削弱了我们预测野生种群适应与存续的能力。